Current and Emerging Adsorbent Technologies for Wastewater Treatment: Trends, Limitations, and Environmental Implications

Removal of food dyes using biological materials via adsorption: A review

It is alarming that synthetic food dyes (FD) are widely used in various industries and that these facilities discharge their wastewater into the environment without treating it. FDs mixed into industrial wastewater pose a threat to the environment and human health. Therefore, removing FDs from wastewater is very important. This review explores the burgeoning field of FD removal from wastewater through adsorption using biological materials (BMs). By synthesizing a wealth of research findings, this comprehensive review elucidates the diverse array of BMs employed, ranging from algae and fungi to agricultural residues and microbial biomass. Furthermore, this review investigates challenges in practical applications, such as process optimization and scalability, offering insights into bridging the gap between laboratory successes and real-world implementations. Harnessing the remarkable adsorptive potential of BMs, this review presents a roadmap toward transformative solutions for FD removal, promising cleaner and safer production practices in the food and beverage industry.

Modified chitosan: Insight on biomedical and industrial applications

Chitosan (CS), a by -product of chitin deacetylation can be useful in a broad range of purposes, to mention agriculture, pharmaceuticals, material science, food and nutrition, biotechnology and of recent, in gene therapy. Chitosan is a highly desired biomolecule due to the existence of many sensitive functional groups inside the molecule and also because of its net cationicity. The latter provides flexibility for creating a wide range of derivatives for particular end users across various industries. This overview aims to compile some of the most recent research on the bio-related applications that chitosan and its derivatives can be used for. However, chitosan's reactive functional groups are amendable to chemical reaction. Modifying the material to show enhanced solubility, a greater range of application options and pH-sensitive targeting and others have been a major focus of chitosan research. This review describes the modifications of chitosan that have been made to improve its water solubility, pH sensitivity, and capacity to target chitosan derivatives. Applying the by-products of chitosan as antibacterial, in targeting, extended release and as delivery systems is also covered. The by-products of chitosan will be important and potentially useful in developing new biomedical drugs in time to come.

Comparing Conventional and Advanced Approaches for Heavy Metal Removal in Wastewater Treatment: An In-Depth Review Emphasizing Filter-Based Strategies

Various industrial activities release heavy metal ions into the environment, which represent one of the major toxic pollutants owing to their severe effects on the environment, humans, and all living species. Despite several technological advances and breakthroughs, wastewater treatment remains a critical global issue. Traditional techniques are dedicated to extracting heavy metal ions from diverse wastewater origins, encompassing coagulation/flocculation, precipitation, flotation, and ion exchange. Their cost, side toxicity, or ineffectiveness often limit their large-scale use. Due to their adaptable design, simple operation, and reasonable cost, membrane filtration and adsorption have proven their efficiency in removing metals from wastewater. Recently, adsorption-based filters have appeared promising in treating water. Within this range, filters incorporating natural, synthetic, or hybrid adsorbents present an appealing alternative to conventional approaches. This review aims to list and describe the conventional and advanced wastewater treatment methods by comparing their efficiency, cost, and environmental impact. Adsorption-based filters were highlighted due to the significant advantages they can provide.

Valorization of food waste: A comprehensive review of individual technologies for producing bio-based products

BACKGROUND

The escalating global concerns about food waste and the imperative need for sustainable practices have fuelled a burgeoning interest in the valorization of food waste. This comprehensive review delves into various technologies employed for converting food waste into valuable bio-based products. The article surveys individual technologies, ranging from traditional to cutting-edge methods, highlighting their respective mechanisms, advantages, and challenges.

SCOPE AND APPROACH

The exploration encompasses enzymatic processes, microbial fermentation, anaerobic digestion, and emerging technologies such as pyrolysis and hydrothermal processing. Each technology's efficacy in transforming food waste into bio-based products such as biofuels, enzymes, organic acids, prebiotics, and biopolymers is critically assessed. The review also considers the environmental and economic implications of these technologies, shedding light on their sustainability and scalability. The article discusses the role of technological integration and synergies in creating holistic approaches for maximizing the valorization potential of food waste. Key finding and conclusion: This review consolidates current knowledge on the valorization of food waste, offering a comprehensive understanding of individual technologies and their contributions to the sustainable production of bio-based products. The synthesis of information presented here aims to guide researchers, policymakers, and industry stakeholders in making informed decisions to address the global challenge of food waste while fostering a circular and eco-friendly economy.

Surface Modifications of Superparamagnetic Iron Oxide Nanoparticles with Chitosan, Polyethylene Glycol, Polyvinyl Alcohol, and Polyvinylpyrrolidone as Methylene Blue Adsorbent Beads

Due to the negative impacts the dye may have on aquatic habitats and human health, it is often found in industrial effluent and poses a threat to public health. Hence, to solve this problem, this study developed magnetic adsorbents that can remove synthetic dyes like methylene blue. The adsorbent, in the form of beads, consists of a polymer blend of chitosan, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, and superparamagnetic iron oxide nanoparticles (average size of 19.03 ± 4.25 nm). The adsorption and desorption of MB from beads were carried out at pH values of 7 and 3.85, respectively. At a concentration of 9 mg/L, the loading capacity and the loading amount of MB after 5 days peaked at 29.75 ± 1.53% and 297.48 ± 15.34 mg/g, respectively. Meanwhile, the entrapment efficiency of MB reached 29.42 ± 2.19% at a concentration of 8 mg/L. The cumulative desorption capacity of the adsorbent after 13 days was at its maximum at 7.72 ± 0.5%. The adsorption and desorption kinetics were evaluated.

An Oxalato-Bridged Cu(II)-Based 1D Polymer Chain: Synthesis, Structure, and Adsorption of Organic Dyes

In the current research, we prepared a polymeric framework, {[Cu(C2O4)(C10H8N2)]·H2O·0.67(CH3OH)]}n (1) (where C2O4 = oxalic acid; C10H8N2 = 2,2-bipyridine), and explored this compound for adsorption of methylene blue (MB) and methyl orange (MO). The crystal structure of the compound consists of a Cu(ox)(bpy) unit connected via oxalate to form a 1D polymeric chain. This polymeric chain has adsorption capacities of 194.0 and 167.3 mg/g for MB and MO, respectively. The removal rate is estimated to be 77.6% and 66.9% for MB and MO, respectively. The plausible mechanisms for adsorption are electrostatic, π-π interaction, and OH-π interaction for dye stickiness. The adsorbent surface exhibits a negative charge that produces the electrostatic interaction, resulting in excellent adsorption efficiency at pH 7 and 8. The pseudo-first-order kinetic model is selected for the adsorption of MB and MO on the adsorbent. The reported compound has remarkable efficiency for sorption of organic dyes and can be useful in wastewater treatment.

Molecular Simulation Studies of Pharmaceutical Pollutant Removal (Rosuvastatin and Simvastatin) Using Novel Modified-MOF Nanostructures (UIO-66, UIO-66/Chitosan, and UIO-66/Oxidized Chitosan)

The ubiquitous presence of pharmaceutical pollutants in the environment significantly threatens human health and aquatic ecosystems. Conventional wastewater treatment processes often fall short of effectively removing these emerging contaminants. Therefore, the development of high-performance adsorbents is crucial for environmental remediation. This research utilizes molecular simulation to explore the potential of novel modified metal-organic frameworks (MOFs) in pharmaceutical pollutant removal, paving the way for the design of efficient wastewater treatment strategies. Utilizing UIO-66, a robust MOF, as the base material, we developed UIO-66 functionalized with chitosan (CHI) and oxidized chitosan (OCHI). These modified MOFs' physical and chemical properties were first investigated through various characterization techniques. Subsequently, molecular dynamics simulation (MDS) and Monte Carlo simulation (MCS) were employed to elucidate the adsorption mechanisms of rosuvastatin (ROSU) and simvastatin (SIMV), two prevalent pharmaceutical pollutants, onto these nanostructures. MCS calculations demonstrated a significant enhancement in the adsorption energy by incorporating CHI and OCHI into UIO-66. This increased ROSU from -14,522 to -16,459 kcal/mol and SIMV from -17,652 to -21,207 kcal/mol. Moreover, MDS reveals ROSU rejection rates in neat UIO-66 to be at 40%, rising to 60 and 70% with CHI and OCHI. Accumulation rates increase from 4 Å in UIO-66 to 6 and 9 Å in UIO-CHI and UIO-OCHI. Concentration analysis shows SIMV rejection surges from 50 to 90%, with accumulation rates increasing from 6 to 11 Å with CHI and OCHI in UIO-66. Functionalizing UIO-66 with CHI and OCHI significantly enhanced the adsorption capacity and selectivity for ROSU and SIMV. Abundant hydroxyl and amino groups facilitated strong interactions, improving performance over that of unmodified UIO-66. Surface functionalization plays a vital role in customizing the MOFs for pharmaceutical pollutant removal. These insights guide next-gen adsorbent development, offering high efficiency and selectivity for wastewater treatment.

Isolation and characterization of Stenotrophomonas pavanii GXUN74707 with efficient flocculation performance and application in wastewater treatment

The identification of microorganisms with excellent flocculants-producing capability and optimization of the fermentation process are necessary for the wide-scale application of bioflocculants. Therefore, we isolated and identified a highly efficient flocculation performance strain of Stenotrophomonas pavanii GXUN74707 from the sludge. The optimal fermentation and flocculation conditions of strain S. pavanii GXUN74707 was in fermentation medium with glucose and urea as the carbon and nitrogen sources, respectively, at pH 7.0 for 36 h, which treatment of kaolin suspension with 0.5 mL of the fermentation broth resulted in a flocculation rate of 99.0%. The bioflocculant synthesized by strain S. pavanii GXUN74707 was found mainly in the supernatant of the fermentation broth. Chemical analysis revealed that the pure bioflocculant consisted of 79.70% carbohydrates and 14.38% proteins. The monosaccharide components of MBF-GXUN74707 are mainly mannose (5.96 μg/mg), galactose (1.86 μg/mg), and glucose (1.73 μg/mg). Infrared spectrometric analysis showed the presence of carboxyl (COO-), hydroxyl (-OH) groups. The SEM images showed clumps of rod-shaped bacteria with adhesion of extracellular products. Furthermore, the strain decolored dye wastewater containing direct black, direct blue, and Congo red by 89.2%, 95.1%, 94.1%, respectively. The chemical oxygen demand (COD) and biological oxygen demand (BOD) removal rates after treatment of aquaculture wastewater with the fermentation broth were 68% and 23%, respectively. This study is the first to report the performance and application of strain Stenotrophomonas pavanii in wastewater flocculation. The results indicate that strain S. pavanii is a good candidate for the production novel bioflocculants and demonstrates its potential industrial practicality in biotechnology processes.

Research on Green Adsorbents

Adsorption processes play a crucial role in air purification, wastewater treatment, soil remediation technologies, noble metals recovery, and long-term energy storage systems [...].

Highly efficient degradation of basic dyes using gold-coated nature-based supermagnetic iron oxide nanoparticles as eco-friendly nanocatalysts

Nowadays, organic dyes are prevalent components in wastewater discharges due to their extensive use in various industries, posing a significant threat to public health across different organisms. As a result, wastewater treatment has become an indispensable requirement. In this study, we synthesized supermagnetic iron oxide (Fe3O4 NPs) and gold-iron oxide bimetallic nanoparticles (Au@Fe3O4 BNPs) using an eco-friendly method that involved natural compounds extracted from brown Egyptian propolis. We employed UV-visible spectroscopy, FTIR, XRD, VSM, SEM, HRTEM, EDX, Zeta potential and XPS techniques to examine the optical characteristics, chemical structure, crystalline structure, magnetic properties, morphology, size, and chemical composition of these biosynthesized nanoparticles. Furthermore, these nanoparticles were used as nanocatalysts for the removal of cationic dyes. The photocatalytic results indicated high efficiency in the removal of methylene blue (MB), crystal violet (CV), and malachite green (MG) dyes from aqueous solutions using Fe3O4 NPs and Au@Fe3O4 BNPs. The removal rates of MB, CV, and MG were about 95.2% in 70 min, 99.4% in 50 min, and 96.2% in 60 min for Fe3O4 NPs, and 97.1% in 50 min, 99.1% in 30 min, and 98.1% in 50 min for Au@Fe3O4 BNPs, respectively. The study also assessed the potential anti-radical properties of the extract, Fe3O4 NPs, and Au@Fe3O4 BNPs using the DPPH assay, and the results demonstrated their antioxidant activity. Finally, these Fe3O4 NPs and Au@Fe3O4 BNPs have the potential to serve as efficient antioxidants and photocatalysts for removing basic dyes from water.

Divergent responses of phosphorus solubilizing bacteria with P-laden biochar for enhancing nutrient recovery, growth, and yield of canola (Brassica napus L.)

The growing global population has led to a heightened need for food production, and this rise in agricultural activity is closely tied to the application of phosphorus-based fertilizers, which contributes to the depletion of rock phosphate (RP) reserves. Considering the limited P reserves, different approaches were conducted previously for P removal from waste streams, while the adsorption of ions is a novel strategy with more applicability. In this study, a comprehensive method was employed to recover phosphorus from wastewater by utilizing biochar engineered with minerals such as calcium, magnesium, and iron. Elemental analysis of the wastewater following a batch experiment indicated the efficiency of the engineered biochar as an adsorbent. Subsequently, the phosphorus-enriched biochar, hereinafter (PL-BCsb), obtained from the wastewater, underwent further analysis through FTIR, XRD, and nutritional assessments. The results revealed that the PL-BCsb contained four times higher (1.82%) P contents which further reused as a fertilizer supplementation for Brassica napus L growth. PL-BCsb showed citric acid (34.03%), Olsen solution (10.99%), and water soluble (1.74%) P desorption. Additionally, phosphorous solubilizing bacteria (PSB) were incorporated with PL-BCsb along two P fertilizer levels P45 (45 kg ha-1) and P90 (90 kg ha-1) for evaluation of phosphorus reuse efficiency. Integrated application of PL-BCsb with half of the suggested amount of P45 (45 kg ha-1) and PSB increased growth, production, physiological, biochemical, and nutritional qualities of canola by almost two folds when compared to control. Similarly, it also improved soil microbial biomass carbon up to four times, alkaline and acid phosphatases activities both by one and half times respectively as compared to control P (0). Furthermore, this investigation demonstrated that waste-to-fertilizer technology enhanced the phosphorus fertilizer use efficiency by 55-60% while reducing phosphorus losses into water streams by 90%. These results have significant implications for reducing eutrophication, making it a promising approach for mitigating environmental pollution and addressing climate change.

A New Approach of Complexing Polymers Used for the Removal of Cu2+ Ions

This study presents two modified polymers for Cu2+ ion removal from aqueous media. Shredded maize stalk (MC) and a strong-base anionic resin (SAX) were modified with indigo carmine (IC) in order to obtain two different complexing polymers, i.e., IC-MC and SAX-IC. Initially, the complex reaction between IC and Cu2+ in the solution was studied. Additionally, the complex formation Cu2+-IC in liquid solutions was evaluated at different pH ranges of 1.5, 4.0, 6.0, 8.0, and 10.0, respectively. For Cu2+ ions, adsorption onto the IC-MC and IC-SAX batch experiments were conducted. The contact time for evaluating the optimum adsorption for Cu2+ ions on the complexing materials was established at 1 h. Efficient Cu2+ ion adsorption on the IC-MC and SAX-IC at pH = 10 was achieved. The adsorption of Cu2+ ions depends on the quantity of IC retained on MC and SAX. At 2.63 mg IC/g MC(S4) and 22 mg IC/g SAX(SR2), a high amount of Cu2+ ion adsorption was reported. The highest adsorption capacity (Qe) of IC-MC was obtained at 0.73 mg/g, and for IC-SAX, it was attained at 10.8 mg/g. Reusability experiments were performed using the HCl (0.5 M) solution. High regeneration and reusability studies of IC-MC and IC-SAX were confirmed, suggesting that they can be used many times to remove Cu2+ ions from aqueous matrices. Therefore, the development of complexing materials could be suitable for Cu2+ ion removal from wastewater.

Advanced oxidation and biological integrated processes for pharmaceutical wastewater treatment: A review

The stress of pharmaceutical and personal care products (PPCPs) discharging to water bodies and the environment due to increased industrialization has reduced the availability of clean water. This poses a potential health hazard to animals and human life because water contamination is a great issue to the climate, plants, humans, and aquatic habitats. Pharmaceutical compounds are quantified in concentrations ranging from ng/Lto μg/L in aquatic environments worldwide. According to (Alsubih et al., 2022), the concentrations of carbamazepine, sulfamethoxazole, Lutvastatin, ciprofloxacin, and lorazepam were 616-906 ng/L, 16,532-21635 ng/L, 694-2068 ng/L, 734-1178 ng/L, and 2742-3775 ng/L respectively. Protecting and preserving our environment must be well-driven by all sectors to sustain development. Various methods have been utilized to eliminate the emerging pollutants, such as adsorption and biological and advanced oxidation processes. These methods have their benefits and drawbacks in the removal of pharmaceuticals. Successful wastewater treatment can save the water bodies; integrating green initiatives into the main purposes of actor firms, combined with continually periodic awareness of the current and potential implications of environmental/water pollution, will play a major role in water conservation. This article reviews key publications on the adsorption, biological, and advanced oxidation processes used to remove pharmaceutical products from the aquatic environment. It also sheds light on the pharmaceutical adsorption capability of adsorption, biological and advanced oxidation methods, and their efficacy in pharmaceutical concentration removal. A research gap has been identified for researchers to explore in order to eliminate the problem associated with pharmaceutical wastes. Therefore, future study should focus on combining advanced oxidation and adsorption processes for an excellent way to eliminate pharmaceutical products, even at low concentrations. Biological processes should focus on ideal circumstances and microbial processes that enable the simultaneous removal of pharmaceutical compounds and the effects of diverse environments on removal efficiency.

A critical review on the separation of heavy metal(loid)s from the contaminated water using various agricultural wastes

Wastewater contamination with heavy metal(loids)s has become a worldwide environmental and public health problem due to their toxic and non-degradable nature. Different methods and technologies have been applied for water/wastewater treatment to mitigate heavy metal(loid)-induced toxicity threat to humans. Among various treatment methods, adsorption is considered the most attractive method because of its high ability and efficiency to remove contaminants from wastewater. Agricultural waste-based adsorbents have gained great attention because of high efficiency to heavy metal(loids)s removal from contaminated water. Chemically modified biosorbents can significantly enhance the stability and adsorption ability of the sorbents. The two mathematical models of sorption, Freundlich and Langmuir isotherm models, have mostly been studied. In kinetic modeling, pseudo-second-order model proved better in most of the studies compared to pseudo-first-order model. The ion exchange and electrostatic attraction are the main mechanisms for adsorption of heavy metal(loid)s on biosorbents. The regeneration has allowed various biosorbents to be recycled and reused up to 4-5 time. Most effective eluents used for regeneration are dilute acids. For practical perspective, biosorbent removal efficiency has been elucidated using various types of wastewater and economic analysis studies. Economic analysis of adsorption process using agricultural waste-based biosorbents proved this approach cheaper compared to traditional commercial adsorbents, such as chemically activated carbon. The review also highlights key research gaps to advance the scope and application of waste peels for the remediation of heavy metal(loid)s-contaminated wastewater.

Sustainable bioremediation technologies for algal toxins and their ecological significance

The emergence of algal toxins in water ecosystems poses a significant ecological and human health concern. These toxins, produced by various algal species, can lead to harmful algal blooms, and have far-reaching consequences on biodiversity, food chains, and water quality. This review explores the types and sources of algal toxins, their ecological impacts, and the associated human health risks. Additionally, the review delves into the potential of bioremediation strategies to mitigate the effects of algal toxins. It discusses the role of microorganisms, enzymes, and algal-bacterial interactions in toxin removal, along with engineering approaches such as advanced oxidation processes and adsorbent utilization. Microbes and enzymes have been studied for their environmentally friendly and biocompatible properties, which make them useful for controlling or removing harmful algae and their toxins. The challenges and limitations of bioremediation are examined, along with case studies highlighting successful toxin control efforts. Finally, the review outlines future prospects, emerging technologies, and the need for continued research to effectively address the complex issue of algal toxins and their ecological significance.

Facile synthesis of ZnO/Hal nanocomposite for arsenite (As(III)) removal from aqueous media

Arsenite (As(III)) is the most toxic form of arsenic that is a serious concern for water contamination worldwide. Herein a ZnO/Halloysite (Hal) nanocomposite was prepared by the chemical bath deposition method (CBD) through seed-mediated ZnO growth on the halloysite for eliminating As(III) from the aqueous solution. The growth of ZnO on seeded halloysite was investigated based on the HMTA: Zn2+ molar ratio in the solution. An optimum molar ratio of HMTA:Zn for nucleation and growth of ZnO upon halloysite was obtained 1:2 based on morphological analysis. The TGA results confirmed that thermal stability of HNT was enhanced by ZnO decoration. The prepared ZnO/Hal nanocomposite at optimal conditions was employed for arsenite (As(III)) removal from aqueous solutions. Experimental data were evaluated with different isothermal, thermodynamic, and kinetic models. Based on the zeta potential results, Hal nanocomposites had a greater negative value than pure Hal. Therefore, the ZnO/Hal nanocomposite exhibited efficient As(III) adsorption with a removal efficiency of 76% compared to pure Hal with a removal efficiency of 5%. Adsorption isotherm was well correlated by both non-linear Langmuir and Sips models, exhibiting maximum adsorption capacity of As(III) at 42.07 mg/g, and 42.5 mg/g, respectively. As a result of the study, it was found that the fabricated Hal nanocomposite with low toxicity can be used effectively in water treatment.

Occurrence, toxicity, impact and removal of selected non-steroidal anti-inflammatory drugs (NSAIDs): A review

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most frequently used pharmaceuticals for human therapy, pet therapeutics, and veterinary feeds, enabling them to enter into water sources such as wastewater, soil and sediment, and seawater. The control of NSAIDs has led to the advent of the novel materials for treatment techniques. Herein, we review the occurrence, impact and toxicity of NSAIDs against aquatic microorganisms, plants and humans. Typical NSAIDs, e.g., ibuprofen, ketoprofen, diclofenac, naproxen and aspirin were detected at high concentrations in wastewater up to 2,747,000 ng L-1. NSAIDs in water could cause genotoxicity, endocrine disruption, locomotive disorders, body deformations, organs damage, and photosynthetic corruption. Considering treatment methods, among adsorbents for removal of NSAIDs from water, metal-organic frameworks (10.7-638 mg g-1) and advanced porous carbons (7.4-400 mg g-1) were the most robust. Therefore, these carbon-based adsorbents showed promise in efficiency for the treatment of NSAIDs.

Green synthesis of a mesoporous hyper-cross-linked polyamide/polyamine 3D network through Michael addition for the treatment of heavy metals and organic dyes contaminated wastewater

Environmental pollution is the greatest challenge of the modern age due to unprecedented industrialization and urbanization that has led to the contamination of water resources with a wide range of pollutants. The release of untreated industrial and municipal wastewater to water bodies further intensifies the problem. The presence of heavy metals and organic contaminants in water poses significant threats to humans, aquatic life, and the environment. Adsorption is one of the famous water treatment technologies due to its simplicity, low cost, efficiency, and minimal secondary pollution. The selection or synthesis of an effective adsorbent is key to the success of the adsorptive removal of pollutants. In this work, we synthesized an adsorbent consisting of a mesoporous hyper-cross-linked polyamide/polyamine 3D network through a single-step Michael addition reaction. The adsorbent was characterized by FTIR, PXRD, TGA, SEM, and TEM to investigate its functional moieties, material nature, thermal, morphological, and internal structural features, respectively. Due to its mesoporous structure, presence of functional groups, and 3D hyper-cross-linked network, it efficiently removed heavy metals (Cd, Cr, and Pb) from aqueous media. The effect of various parameters such as sample pH, adsorbent dosage, contact time, and adsorbate concentrations was thoroughly investigated. The experimental data were analyzed by a variety of isotherm models wherein Langmuir was found to be the best fit for explaining the adsorption of all the metals. The adsorption kinetics was best explained by the pseudo-second-order model. The maximum adsorption capacities for Cd, Cr, and Pb were 60.98 mg g-1, 119 mg g-1, and 9.302 mg g-1, respectively. The synthesized adsorbent was also tested for removal of organic dyes, and it showed selective and fast removal of Eriochrome Black T. Polymeric resins can be promising materials for adsorptive remediation of pollutants in aqueous media.

Recent Advances in Microbial-Assisted Remediation of Cadmium-Contaminated Soil

Soil contamination with cadmium (Cd) is a severe concern for the developing world due to its non-biodegradability and significant potential to damage the ecosystem and associated services. Industries such as mining, manufacturing, building, etc., rapidly produce a substantial amount of Cd, posing environmental risks. Cd toxicity in crop plants decreases nutrient and water uptake and translocation, increases oxidative damage, interferes with plant metabolism and inhibits plant morphology and physiology. However, various conventional physicochemical approaches are available to remove Cd from the soil, including chemical reduction, immobilization, stabilization and electro-remediation. Nevertheless, these processes are costly and unfriendly to the environment because they require much energy, skilled labor and hazardous chemicals. In contrasting, contaminated soils can be restored by using bioremediation techniques, which use plants alone and in association with different beneficial microbes as cutting-edge approaches. This review covers the bioremediation of soils contaminated with Cd in various new ways. The bioremediation capability of bacteria and fungi alone and in combination with plants are studied and analyzed. Microbes, including bacteria, fungi and algae, are reported to have a high tolerance for metals, having a 98% bioremediation capability. The internal structure of microorganisms, their cell surface characteristics and the surrounding environmental circumstances are all discussed concerning how microbes detoxify metals. Moreover, issues affecting the effectiveness of bioremediation are explored, along with potential difficulties, solutions and prospects.

Microalgae biofilm system as an efficient tool for wastewater remediation and potential bioresources for pharmaceutical product production: an overview

The role of microalgae in wastewater remediation and metabolite production has been well documented, but the limitations of microalgae harvesting and low biomass production call for a more sustainable method of microalgae utilization. The current review gives an insight on how microalgae biofilms can be utilized as a more efficient system for wastewater remediation and as potential source of metabolite for pharmaceutical product production. The review affirms that the extracellular polymeric substance (EPS) is the vital component of the microalgae biofilm because it influences the spatial organization of the organisms forming microalgae biofilm. The EPS is also responsible for the ease interaction between organisms forming microalgae biofilm. This review restate the crucial role play by EPS in the removal of heavy metals from water to be due to the presence of binding sites on its surface. This review also attribute the ability of microalgae biofilm to bio-transform organic pollutant to be dependent on enzymatic activities and the production of reactive oxygen species (ROS). The review assert that during the treatment of wastewater, the wastewater pollutants induce oxidative stress on microalgae biofilms. The response of the microalgae biofilm toward counteracting the stress induced by ROS leads to production of metabolites. These metabolites are important tools that can be harness for the production of pharmaceutical products.

Copper Accumulation Efficiency in Different Recombinant Microorganism Strains Available for Bioremediation of Heavy Metal-Polluted Waters

The aim of this research was to investigate the bioremediation conditions of copper in synthetic water. In the present study, copper ions accumulation efficiency was determined using various genetically modified strains of Saccharomyces cerevisiae (EBY100, INVSc1, BJ5465, and GRF18), Pichia pastoris (X-33, KM71H), Escherichia coli (XL10 Gold, DH5α, and six types of BL21 (DE3)), and Escherichia coli BL21 (DE3) OverExpress expressing two different peroxidases. Viability tests of yeast and bacterial strains showed that bacteria are viable at copper concentrations up to 2.5 mM and yeasts up to 10 mM. Optical emission spectrometry with inductively coupled plasma analysis showed that the tolerance of bacterial strains on media containing 1 mM copper was lower than the tolerance of yeast strains at the same copper concentration. The E. coli BL21 RIL strain had the best copper accumulation efficiency (4.79 mg/L of culture normalized at an optical density of 1.00), which was 1250 times more efficient than the control strain. The yeast strain S. cerevisiae BJ5465 was the most efficient in copper accumulation out of a total of six yeast strains used, accumulating over 400 times more than the negative control strain. In addition, E. coli cells that internally expressed recombinant peroxidase from Thermobifida fusca were able to accumulate 400-fold more copper than cells that produced periplasmic recombinant peroxidases.

Microbial biosorbent for remediation of dyes and heavy metals pollution: A green strategy for sustainable environment

Toxic wastes like heavy metals and dyes are released into the environment as a direct result of industrialization and technological progress. The biosorption of contaminants utilizes a variety of biomaterials. Biosorbents can adsorb toxic pollutants on their surface through various mechanisms like complexation, precipitation, etc. The quantity of sorption sites that are accessible on the surface of the biosorbent affects its effectiveness. Biosorption’s low cost, high efficiency, lack of nutrient requirements, and ability to regenerate the biosorbent are its main advantages over other treatment methods. Optimization of environmental conditions like temperature, pH, nutrient availability, and other factors is a prerequisite to achieving optimal biosorbent performance. Recent strategies include nanomaterials, genetic engineering, and biofilm-based remediation for various types of pollutants. The removal of hazardous dyes and heavy metals from wastewater using biosorbents is a strategy that is both efficient and sustainable. This review provides a perspective on the existing literature and brings it up-to-date by including the latest research and findings in the field.

Chitosan-Based Architectures as an Effective Approach for the Removal of Some Toxic Species from Aqueous Media

Modified uncrosslinked and crosslinked chitosan derivatives were investigated as green sorbents for the removal of copper (Cu²⁺) and lead (Pb²⁺) cations from simulated solutions. In this regard, N, O carboxymethyl chitosan (N, O CMC), chitosan beads (Cs-g-GA), chitosan crosslinked with glutaraldehyde/methylene bisacrylamide (Cs/GA/MBA), and chitosan crosslinked with GA/epichlorohydrin (Cs/GA/ECH) were prepared and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy analyses. Atomic force microscopy investigation was carried out to compare the surface topography of the prepared samples before and after the metal uptake. The kinetics of the removal process were investigated by pseudo-first-order and -second-order models. Moreover, the adsorption isotherms were carefully studied by applying Langmuir and Freundlich models. The data reveal that upon adsorption of copper(II) metal ions, all chitosan-modified products followed the Langmuir isotherm except for Cs/GA/ECH which followed the Freundlich isotherms, and the highest adsorption capacity (q _e) was obtained for Cs/GA/MBA due to the formation of stable chelate structures between the metal cation and the functional groups present on the modified chitosan product. The order of metal uptake at the optimum pH value is as follows: Cs/GA/MBA (Cu: 95.7 mg/g, Pb: 99.15 mg/g), Cs/GA/ECH (Cu: 80.4 mg/g, Pb: 93.14 mg/g), Cs-g-GA (Cu: 77 mg/g, Pb: 88.4 mg/g), and N, O CMCh (Cu: 30.2 mg/g, Pb: 44.8 mg/g). The AFM data confirmed the metal uptake process by comparing the roughness and height measurements of the free sorbents and the metal-loaded sorbents.

Durian Waste Husks as an Adsorbent in Improving Soaking Water during the Retting Process of Piper nigrum L. (Pepper Berries)

The potential of raw durian husk and NaOH-modified durian husk as an adsorbent, using different doses, 0.5 g, 1.0 g, 1.5 g, and 2.0 g, is investigated to improve soaking water of pepper berries during the retting process. The surface area and the pore size of the durian husk were examined using Brunner Emmett and Teller analysis. The surface area of NaOH-modified durian husk is higher (2.33 m2/g) compared to the raw durian husk (1.51 m2/g). NaOH-modified durian husk has a higher porous structure than the raw durian husk, but both pore diameters are more than 50 nm, which is considered micropore raw material. The effect of the raw durian husk on pH, chemical oxygen demand (COD), dissolved oxygen (DO), and turbidity were compared to the NaOH-modified durian husk with different doses. The 2.0 g of NaOH-modified durian husk enhanced changes in the four parameters. The highest pH value using NaOH-modified durian husk was 6.10 ± 0.02, while turbidity and COD increased to 971.33 ± 1.15 NTU and 1984.67 ± 3.21 mg/L, respectively. The DO of NaOH-modified durian husk shows the lowest reduction to 1.49 mg/L with 2.0 g of NaOH-modified durian husk. The experimental data was best fitted with a first-order kinetic model. Durian husk treated with NaOH could be used as a potential adsorbent to enhance the soaking water for pepper berries.

The versatility of nanocellulose, modification strategies, and its current progress in wastewater treatment and environmental remediation

Deterioration in the environmental ecosystems through the depletion of nonrenewable resources and the burden of deleterious contaminants is considered a global concern. To this end, great interest has been shown in the use of renewable and environmentally-friendly reactive materials dually to promote environmental sustainability and cope with harmful contaminants. Among the different available options, the use of nanocellulose (NC) as an environmentally benign and renewable natural nanomaterial is an attractive candidate for environmental remediation owing to its miraculous physicochemical characteristics. This review discusses the intrinsic properties and the structural aspects of different types of NC, including cellulose nanofibrils (CNFs), cellulose nanocrystals (CNCs), and bacterial cellulose (BC) or bacterial nanocellulose (BNC). Also, the different modification strategies involving the functionalization or hybridization of NC by using different functional and reactive materials aimed at wastewater remediation have been elaborated. The modified or hybridized NC has been explored for its applications in the removal or degradation of aquatic contaminants through adsorption, filtration, coagulation, catalysis, photocatalysis, and pollutant sensing. This review highlights the role of NC in the modified composites and describes the underlying mechanisms involved in the removal of contaminants. The life-cycle assessment (LCA) of NC is discussed to unveil the hidden risks associated with its production to the final disposal. Moreover, the contribution of NC in the promotion of waste management at different stages has been described in the form of the five-Rs strategy. In summary, this review provides rational insights to develop NC-based environmentally-friendly reactive materials for the removal and degradation of hazardous aquatic contaminants.

Water Cleaning by a Continuous Fixed-Bed Column for Cr(VI) Eco-Adsorption with Green Adsorbent-Based Biomass: An Experimental Modeling Study

In this study, chromate adsorption onto red peanut skin (RPS) was investigated in a fixed-bed column; FTIR, PZC, SEM, DLS, and BET were used to evaluate its adsorption properties. The experiments were conducted to determine the effect of physical parameters, including the inlet initial Cr(VI) concentration (100–500 mg L−1), bed height (10–20 cm), and feed flow rate (13.59–23.45 mL min−1). They were carried out to predict breakthrough curves. The adsorption capacity coefficients were determined using the most widely used Bohart–Adams model. It was tested to fit experimental data, for a better understand the dynamic behavior, and for further optimize column performance. It was found that the Cr(VI) uptake decreases when increasing the flow rate and that high chromate concentration and bed height consequently increase the column’s life span. A high column adsorption capacity can be achieved with a higher Cr(VI) concentration due to the higher driving force. The results indicated that the Bohart–Adams model provides a good description (R2 > 0.98) of the experimental data of the Cr(VI)’s removal from the aqueous solution on the RPS suggesting that the surface diffusion is the rate-limiting step in the continues adsorption process.. Breakthrough adsorption capacity is crucial for comparing RPS with other similar materials. Indeed, possible mechanisms have been suggested for illustrating adsorption onto RPS. The obtained results showed significant potential of 26.23 mg g−1 of RPS on Cr(VI) elimination at a natural pH of 5.35. Furthermore, this global investigation allowed for the design of a promising low-cost material for the future scale-up of cleaning wastewater polluted by metal and determine the properly conditions for operating column adsorption. This material provides an economical, efficient means of eliminating pollutants, thus meeting the main aims of the UN Sustainable Development Goals (UN SDGs).

Oxygen Vacancy-Mediated Activates Oxygen to Produce Reactive Oxygen Species (ROS) on Ce-Modified Activated Clay for Degradation of Organic Compounds without Hydrogen Peroxide in Strong Acid

The treatment of acid wastewater to remove organic matter in acid wastewater and recycle valuable resources has great significance. However, the classical advanced oxidation process (AOPs), such as the Fenton reaction, encountered a bottleneck under the conditions of strong acid. Herein, making use of the oxidation properties of CeAY (CeO₂@acid clay), we built an AOPs reaction system without H₂O₂ under a strong acid condition that can realize the transformation of organic matter in industrial wastewater. The X-ray photoelectron spectroscopy (XPS) proved that the CeAY based on Ce³⁺ as an active center has abundant oxygen vacancies, which can catalyze O₂ to produce reactive oxygen species (ROS). Based on the electron spin-resonance spectroscopy spectrum and radical trapping experiments, the production of •O₂^- and •OH can be determined, which are the essential factors of the degradation of organic compounds. In the system of pH = 1.0, when 1 mg CeAY is added to 10 mL of wastewater, the degradation efficiency of an aniline solution with a 5 mg/L effluent concentration is 100%, and that of a benzoic acid solution with a 100 mg/L effluent concentration is 50% after 10 min of reaction. This work may provide novel insights into the removal of organic pollutants in a strong acid water matrix.

A review of adsorption techniques for removal of phosphates from wastewater

Phosphate is considered the main cause of eutrophication and has received considerable attention recently. Several methods have been used for removal of phosphates in water and these include biological treatment, membrane filtration processes, chemical precipitation, and adsorption. Adsorption technology is highly effective in the removal of phosphate from wastewater even at low phosphate concentrations. Nanomaterials/nanoparticles, carbon-based materials (activated carbon and biochar), and their composites have been widely employed for the adsorptive removal and recovery of phosphate from wastewater due to their exceptional properties such as high surface area and high phosphate adsorption properties. This article is a review of the recently reported literature in the field of nanotechnology and activated carbon for the adsorption of phosphate from wastewater. Highlights of the adsorption mechanisms, adsorption behaviour, experimental parameters, effects of co-existing ions, and adsorbent modifications are also discussed.

Shaping polyelectrolyte composites for heavy metals adsorption from wastewater: Experimental assessment and equilibrium studies

Design of core/shell composite microparticles for loading/release of organic/inorganic pollutants is of great interest in wastewater treatment. As compared to the classic layer-by-layer strategy, the new approach presented in this study introduced higher organic shell amounts in one-pot deposition step, with less material and energy consumption and lack of toxic by-products formation. Herein, one weak polycation (polyethyleneimine) and two weak polyanions were directly deposited onto silica surface through precipitation of an in-situ formed interpolyelectrolyte coacervate, followed by selective crosslinking with glutaraldehyde and extraction of polyanion chains, confirmed by electrokinetic measurements and FTIR spectra of composites. Twelve composite sorbents were synthesized and tested for adsorption of cadmium, as model heavy metal ion. It was demonstrated that the high sorption occurred onto four newly synthesized composites which is correlated to the deposited shell amount, dependent on the deposition method, polyanion nature and crosslinking ratio. The Cd²⁺ sorbed amount increased with the polyelectrolyte deposited amount and with the accessibility toward active sorption site, less cross-linked composite shells sorbing higher amounts as compared to strong cross-linked shells, the molar ratio [active site]:[Cd²⁺] ranging from 16:1 to 26:1. The best fitting of four isotherm (Langmuir, Freundlich, Sips and Toth) and four kinetics (pseudo-first order, pseudo-second order, modified Freundlich and Elovich) models was assessed by the sum of normalized errors, based on different nonlinear regression error functions, and by the Hannah-Quinn information criterion. In general, the best agreement with the experimental data was found for Toth isotherm and the pseudo-second order kinetic model. Efficient regeneration of the sorbents was possible at least three times. The competitive effect of Pb²⁺ and Ni²⁺ ions was also studied in simulated and real systems. Silica composite sorbents with polyethyleneimine chains as major component of the shell could be very promising in wastewater treatment processes.

Photocatalytic Degradation of Methylene Blue and Ortho-Toluidine Blue: Activity of Lanthanum Composites LaxMOy (M: Fe, Co, Ni)

Lanthanum (La) nanocomposites LaFeO3, LaNiO3, and LaCoO3 were synthesized using a sol-gel method, and different La to-metal (Fe, Ni, or Co) ratios were attained using various concentrations of salts. The resulting composites were calcined at 540 °C and characterized by XRD, SEM-EDX, FT-IR spectroscopy, XPS, thermogravimetric analysis (TGA), and PL spectroscopy. The activity of the lanthanum composites (LaFeO3, LaNiO3, and LaCoO3) was studied using the photocatalytic degradation of methylene blue (MB) and ortho-toluidine blue (o-TB) under visible light with a wavelength below 420 nm. The change in the concentration of dyes was monitored by using the UV-Vis spectroscopy technique. All composites appeared to have some degree of photocatalytic activity, with composites possessing an orthorhombic crystal structure having higher photocatalytic activity. The LaCoO3 composite is more efficient compared with LaFeO3 and LaNiO3 for both dyes. High degradation percentages were observed for the La composites with a 1:1 metal ratio.

Photocatalytic and Electrochemical Activity of Magnesium Oxide Nanoballs Synthesized via a Hydrothermal Route

Currently, there is growing concern about minimizing the environmental impacts caused by the generation of waste on water, soil, air pollution, and contamination of the environment in general. Magnesium oxide (MgO) nanoballs (NBs) were synthesized by the hydrothermal method followed by a calcination process. The average size of particles dispersed in deionized water was 159.2 ± 70 nm. The energy band gap was calculated to be 5.14 eV. The magnetic behavior, cyclic voltammetry, and electrochemical impedance of MgO NBs were studied. Under visible-light irradiation, the photocatalytic activity of MgO nanoballs was investigated by methylene blue (MB) dye. Results showed that photodegradation for MB under visible light irradiation for 120 min and degradation results are fitted well with pseudo-first-order reaction kinetics with a rate constant of 0.00252 min−1 and a correlation coefficient of 0.96.

Enhanced adsorption of Congo red dye onto polyethyleneimine-impregnated biochar derived from pine needles

Biochar derived from waste pine needles was chemically modified using polyethyleneimine (PEI) to increase its adsorptive potential for withdrawal of anionic dye Congo red from aqueous solution. PEI impregnation on biochar was confirmed from scanning electron microscopy and energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The surface area of biochar decreased after PEI treatment, but the amine groups increased on biochar surface. PEI-treated biochar displayed considerable increase in adsorption at acidic conditions. Adsorption isotherm was best explained by Langmuir model (R² > 99) and the adsorption kinetics agrees well with pseudo-second-order model. The maximum adsorption capacity of PEI-treated biochar was observed to be 294.11 mg g^-1 and 30.76 mg g^-1 for pristine biochar displaying a 9.5-fold increase. The positive value of standard enthalpy of adsorption (∆H° = 14.96 KJmole^-1) indicated the endothermic nature of adsorption, and positive value of entropy (∆S° = 74.43 Jmole^-1 K^-1) revealed the affinity of biochar towards dye molecules. Negative value of Gibb's free energy ∆G° (- 7.2 KJmole^-1) revealed that the process was spontaneous. Electrostatic interaction appeared to be the key mechanism governing the adsorption process. Thus, PEI-impregnated biochar represents novel low-cost sorbent that can effectively remove anionic dyes which are poorly removed by pristine biochar.

Adsorption Study of Continuous Heavy Metal Ions (Pb2+, Cd2+, Ni2+) Removal Using Cocoa (Theobroma cacao L.) Pod Husks

The serious toxicological effects of heavy metal ions in aquatic ecosystems have motivated the search for alternatives to reduce contamination of water sources from industrial wastewater. In this work, continuous adsorption of nickel, cadmium, and lead was assessed using a packed bed column filled with Cocoa (Theobroma cacao L.) pod husks widely available in the northern region of Colombia. The physicochemical characterization of the agricultural biomass was performed to quantify its chemical composition by bromatological, FT-IR, and energy-dispersive X-ray spectroscopy (EDS). The breakthrough curves were constructed for all heavy metal ions with bed depth of 4 and 7.5 cm, taking aliquots at 10, 30, 60, 90, 120, 150, 180, 210, 240, and 270 min. Moreover, experimental data were fitted to adsorption models in continuous mode to predict adsorptive performance (Adams−Bohart, Thomas, and Yoon−Nelson). For the FT-IR analysis of biomass before and after adsorption, the most representative bands occur around 3200−3900 cm−1 attributed to the presence of hydroxyl groups, showing the destruction of the peaks of lignocellulosic materials. The breakthrough curves revealed that for a 7.5 cm bed, adsorption performance reported the following order of promising results: Pb2+ > Ni2+ > Cd2+; while for a 4 cm bed, Pb2+ > Ni2+. The mechanism of adsorption of the evaluated metals onto cocoa pod husk was attributed to cationic exchange and microprecipitation due to the presence of Ca, K, and Si in the structure of the bio-adsorbent. Finally, the continuous adsorption was modeled under the mathematical expressions of Adams−Bohart, Thomas, and Yoon−Nelson reporting good fitting with correlation coefficient above 0.95.

Highly effective water hyacinth (Eichhornia crassipes) waste-based functionalized sustainable green adsorbents for antibiotic remediation from wastewater

Azithromycin (AZIM) is considered as one of the most frequently prescribed antibiotics (ABs) in the world by medical professionals. This study explored, two novel, cheap and environmentally beneficial adsorbents i.e., alkali treated water hyacinth powder (AT-WHP) and graphene oxide-water hyacinth-polyvinyl alcohol (GO-WH-PVA) composite, fabricated from water hyacinth (Eichhornia crassipes) waste to remediate AZIM from wastewater. Biosorption experiments were performed by batch and packed-bed column studies and the adsorbents were characterized using various instrumental methods. The morpho-chemical profile of the adsorbents suggested noteworthy AZIM adsorption. AZIM adsorption data can be reasonably explained by pseudo second order (PSO) kinetic model with maximum regression coefficient (R² > 0.99) and lowest Marquardt's present standard deviation (MPSD) and root mean squared error (RMSE) values. The isotherm models recommended Langmuir and Temkin to be the best-fitted, providing highest regression coefficient and lowest error values. Conferring to Langmuir model, the theoretical highest adsorption potentials (q_max) were accounted to be 244.498 and 338.115 mg/g for AT-WHP and GO-WH-PVA, correspondingly, very close to experimental values (q_e, exp). AZIM adsorption processes were governed by the chemisorption mechanisms. The adsorbents had excellent regeneration potential and could be reused several times. In order to scale-up application of the adsorbents, performance of a 100 L packed-bed reactor was assessed and a breakthrough time of adsorption for GO-WH-PVA was 15 min in 5000 mg/L AZIM concentration. Thus, the absorbents synthesized in this study can be considered highly effective at removal of AZIM from wastewater.

A techno-economic approach for eliminating dye pollutants from industrial effluent employing microalgae through microbial fuel cells: Barriers and perspectives

Microbial fuel cells are biochemical factories which besides recycling wastewater are electricity generators, if their low power density can be scaled up. This also adds up to work on many factors responsible to increase the cost of running a microbial fuel cell. As a result, the first step is to use environment friendly dead organic algae biomass or even living algae cells in a microbial fuel cell, also referred to as microalgal microbial fuel cells. This can be a techno-economic aspect not only for treating textile wastewater but also an economical way of obtaining value added products and bioelectricity from microalgae. Besides treating wastewater, microalgae in its either form plays an essential role in treating dyes present in wastewater which essentially include azo dyes rich in synthetic ions and heavy metals. Microalgae require these metals as part of their metabolism and hence consume them throughout the integration process in a microbial fuel cell. In this review a detail plan is laid to discuss the treatment of industrial effluents (rich in toxic dyes) employing microbial fuel cells. Efforts have been made by researchers to treat dyes using microbial fuel cell alone or in combination with catalysts, nanomaterials and microalgae have also been included. This review therefore discusses impact of microbial fuel cells in treating wastewater rich in textile dyes its limitations and future aspects.

Recent Trends in the Preparation of Nano-Starch Particles

Starch is affected by several limitations, e.g., retro-gradation, high viscosity even at low concentrations, handling issues, poor freeze–thaw stability, low process tolerance, and gel opacity. In this context, physical, chemical, and enzymatic methods have been investigated for addressing such limitations or adding new attributes. Thus, the creation of biomaterial-based nanoparticles has sparked curiosity. Because of that, single nucleotide polymorphisms are gaining a lot of interest in food packaging technology. This is due to their ability to increase the mechanical and water vapor resistance of the matrix, as well as hide its re-crystallization during storage in high-humidity atmospheres and enhance the mechanical properties of films when binding in paper machines and paper coating. In medicine, single nucleotide polymorphisms (SNPs) are suitable as carriers in the field of drug delivery for immobilized bioactive or therapeutic agents, as well as wastewater treatments as an alternative to expensive activated carbons. Starch nanoparticle preparations can be performed by hydrolysis via acid hydrolysis of the amorphous part of a starch molecule, the use of enzymes such as pullulanase or isoamylase, or a combination of two regeneration and mechanical treatments with the employment of extrusion, irradiation, ultrasound, or precipitation. The possibility of obtaining cheap and easy-to-use methods for starch and starch derivative nanoparticles is of fundamental importance. Nano-precipitation and ultra-sonication are rather simple and reliable methods for nanoparticle production. The process involves the addition of a diluted starch solution into a non-solvent, and ultra-sonication aims to reduce the size by breaking the covalent bonds in polymeric material due to intense shear forces or mechanical effects associated with the collapsing of micro-bubbles by sound waves. The current study focuses on starch nanoparticle manufacturing, characterization, and emerging applications.

Characterization of Cu(II) and Zn(II) Sorption onto Zeolite

In this study, a batch sorption study approach was combined with an instrumental analytical approach of atomic absorption spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) for the sorption of copper and zinc ions from aqueous solution on zeolites. Both copper and zinc are biogenic elements; nevertheless, many industrial processes produce an excessive amount, which is why their efficient removal from water must be studied. Two types of zeolites, Zeolite Micro 20 (Z-M20) and Zeolite Micro 50 (Z-M50), were used. The results showed that the maximum sorption capacities for removal of Cu and Zn were 1.06 for CuSO4, 42.35 for Cu(NO3)2, 1.15 for ZnSO4 and 2.29 for Zn(NO3)2 adsorption onto Z-M20 and 0.45 for CuSO4, 1.67 for Cu(NO3)2, 0.39 for ZnSO4 and 1.51 for Zn(NO3)2 adsorption onto Z-M50. The maximum sorption capacities are higher for sulfates and the sorbent with smaller particle size. The sorption capacities of Cu and Zn for corresponding anion and particle size differ only up to 5–15%. Using XRD and XPS analyses before and after the sorption process, it was found that the content of both Cu and Zn in the surface layer and the bulk are the same for sorption onto sorbent with smaller particle size, but are higher in the surface layer than in the bulk for sorption onto sorbent with larger particle size. One of the main findings of this study is that a zeolite with smaller particles takes Cu and Zn by the whole particle, while with bigger particles, Cu and Zn concentrate in the surface of the particle. The results of the study may be used as an indicator for sorption efficiency of the studied zeolites for their application in the treatment of copper and zinc contaminated effluents.

Databionic Swarm Intelligence to Screen Wastewater Recycling Quality with Factorial and Hyper-Parameter Non-Linear Orthogonal Mini-Datasets

Electrodialysis (ED) may be designed to enhance wastewater recycling efficiency for crop irrigation in areas where water distribution is otherwise inaccessible. ED process controls are difficult to manage because the ED cells need to be custom-built to meet local requirements, and the wastewater influx often has heterogeneous ionic properties. Besides the underlying complex chemical phenomena, recycling screening is a challenge to engineering because the number of experimental trials must be maintained low in order to be timely and cost-effective. A new data-centric approach is presented that screens three water quality indices against four ED-process-controlling factors for a wastewater recycling application in agricultural development. The implemented unsupervised solver must: (1) be fine-tuned for optimal deployment and (2) screen the ED trials for effect potency. The databionic swarm intelligence classifier is employed to cluster the L9(34) OA mini-dataset of: (1) the removed Na+ content, (2) the sodium adsorption ratio (SAR) and (3) the soluble Na+ percentage. From an information viewpoint, the proviso for the factor profiler is that it should be apt to detect strength and curvature effects against not-computable uncertainty. The strength hierarchy was analyzed for the four ED-process-controlling factors: (1) the dilute flow, (2) the cathode flow, (3) the anode flow and (4) the voltage rate. The new approach matches two sequences for similarities, according to: (1) the classified cluster identification string and (2) the pre-defined OA factorial setting string. Internal cluster validity is checked by the Dunn and Davies–Bouldin Indices, after completing a hyper-parameter L8(4122) OA screening. The three selected hyper-parameters (distance measure, structure type and position type) created negligible variability. The dilute flow was found to regulate the overall ED-based separation performance. The results agree with other recent statistical/algorithmic studies through external validation. In conclusion, statistical/algorithmic freeware (R-packages) may be effective in resolving quality multi-indexed screening tasks of intricate non-linear mini-OA-datasets.

Wastewater Quality Screening Using Affinity Propagation Clustering and Entropic Methods for Small Saturated Nonlinear Orthogonal Datasets

Wastewater recycling efficiency improvement is vital to arid regions, where crop irrigation is imperative. Analyzing small, unreplicated–saturated, multiresponse, multifactorial datasets from novel wastewater electrodialysis (ED) applications requires specialized screening/optimization techniques. A new approach is proposed to glean information from structured Taguchi-type sampling schemes (nonlinear fractional factorial designs) in the case that direct uncertainty quantification is not computable. It uses a double information analysis–affinity propagation clustering and entropy to simultaneously discern strong effects and curvature type while profiling multiple water-quality characteristics. Three water quality indices, which are calculated from real ED process experiments, are analyzed by examining the hierarchical behavior of four controlling factors: (1) the dilute flow, (2) the cathode flow, (3) the anode flow, and (4) the voltage rate. The three water quality indices are: the removed sodium content, the sodium adsorption ratio, and the soluble sodium percentage. The factor that influences the overall wastewater separation ED performance is the dilute flow, according to both analyses’ versions. It caused the maximum contrast difference in the heatmap visualization, and it minimized the relative information entropy at the two operating end points. The results are confirmed with a second published independent dataset. Furthermore, the final outcome is scrutinized and found to agree with other published classification and nonparametric screening solutions. A combination of modern classification and simple entropic methods which are offered through freeware R-packages might be effective for testing high-complexity ‘small-and-dense’ nonlinear OA datasets, highlighting an obfuscated experimental uncertainty.

Comparison Study on Sonodirect and Sonoalternate Current Electrocoagulation Process for Domestic Wastewater Treatment

Nowadays, there is a problem related to wastewater handling which is released from different activities. The electrocoagulation method has been a dominant treatment method for wastewater treatment. There are different forms of electrocoagulation methods for wastewater treatment. Nevertheless, there was no comparison made for the removal efficiency of the sonoalternate current (SAC), alternate current (AC), sonodirect current (SDC), and direct current (DC) electrocoagulation process. The efficiency of electrocoagulation methods was compared for their removal of chemical oxygen demand (COD) from Jimma University domestic wastewater. Batch Reactor DC/AC electrocoagulation cell was used to determine the removal efficiency. During the comparison, the response surface methodology (RSM) was used to analyze and optimize the data taken from the laboratory. Besides, ANOVA was used to analyze the interaction effects of different parameters. The removal of COD from domestic wastewater was achieved with DCE, ACE, SDCE, and SACE which were 82.6%, 86.58%, 88.6%, and 92.5%, respectively, under optimal experimental conditions. From the finding, SACE was more successful at removing % COD than the DCE, ACE, and SDCE methods. For DCE and SDCE, the formation of an impermeable oxide layer at the cathode and the occurrence of corrosion at the anode due to oxidation made the COD removal process less efficient compared with SACE processes. From the experimental results it can be concluded that the SACE has the lowest power consumption and higher process efficiency than the other EC methods and can be a promising solution for removing pollutants from domestic wastewater.

Valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment: Approaching green chemistry and circular economy principles

Water pollution is one of the most critical issues worldwide and is a priority in all scientific agendas. Green nanotechnology presents a plethora of promising avenues for wastewater treatment. This review discusses the current trends in the valorization of zero-cost, biodegradable, and readily available agro-industrial biowaste to produce green bio-nanocatalysts and bio-nanosorbents for wastewater treatment. The promising roles of green bio-nanocatalysts and bio-nanosorbents in removing organic and inorganic water contaminants are discussed. The potent antimicrobial activity of bio-derived nanodisinfectants against water-borne pathogenic microbes is reviewed. The bioactive molecules involved in the chelation and tailoring of green synthesized nanomaterials are highlighted along with the mechanisms involved. Furthermore, this review emphasizes how the valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment adheres to the fundamental principles of green chemistry, circular economy, nexus thinking, and zero-waste manufacturing. The potential economic, environmental, and health impacts of valorizing agro-industrial biowaste to green nanomaterials are highlighted. The challenges and future outlooks for the management of agro-industrial biowaste and safe application of green nanomaterials for wastewater treatment are summarized.

Effect of Freeze-Drying on Apple Pomace and Pomegranate Peel Powders Used as a Source of Bioactive Ingredients for the Development of Functional Yogurt

Agro-industrial by-products of fruits have turned into an essential source of bioactive products. This study examined the effect of freeze-drying on apple pomace powder (APP) and pomegranate peel powder (PPP) and their utilization in functional yogurt development at different concentrations. Freeze-dried powders in functional yogurt were investigated by chemical profile and bioactive characterization of total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity. The highest concentration of TPC (4.64) mg GAE/g, TFC (1.73 ± 0.00) CE mg/g, and antioxidant activity (83.87 ± 0.02) % was investigated in the yogurt sample T6, having the maximum amount of PPP in it, which was significantly higher compared to the treatments having APP. Yogurt samples were analyzed for their sensory attributes, which showed a decline with the increase in both APP and PPP concentrations in contrast by introducing the optimum levels of APP and PPP (3% or 6%); hence, no significant loss in sensory profile was found as compared to the control samples. The results were found to be significant at the level ( $p<0.05$ ). In terms of the freeze-dried APP and PPP results, the APP samples had the most complete chemical composition, with the exception of fiber and ash concentration. Treatments of functional yogurt were prepared for their physicochemical profile, which demonstrated a straight proportionate relationship between the proportions of both powders in the meantime. Protein and fat levels were likely to decrease as both dry powder levels increased. Hence, apple pomace and pomegranate peel can be used after freeze-drying as a rich source of bioactive compounds in functional yogurt in the food industry.

Production and Optimization of Bio-Based Silica Nanoparticle from Teff Straw (Eragrostis tef) Using RSM-Based Modeling, Characterization Aspects, and Adsorption Efficacy of Methyl Orange Dye

The brown teff straw was utilized in this study to produce silica using the sol-gel technique. After pretreatment, the raw material of brown teff straw was characterized. The data were analyzed using the central composite design and response surface technique, and four independent parameters, namely, temperature, NaOH concentration, rotational speed, and extraction time, were evaluated for process optimization. Before extracting silica with an alkaline solution, the silica content in the ash was determined using an AAS spectrometer. The silica content of teff straw ash is around 92.89%. The ash was treated with NaOH solution in the concentrations range of 1 M to 3 M (0.5 M interval). The extraction time varied at intervals of 55, 70, 85, 100, and 115 minutes. Temperatures were changed using magnetic stirrer equipment in the range of 80°C to 100°C (5°C interval). At 350 rpm, 400 rpm, 450 rpm, 500 rpm, and 550 rpm, the rotating speed was adjusted. The best extraction conditions for amorphous silica were 1.50 M NaOH, 109.99 min, 94.98°C, and a rotating speed of 499.57 rpm, with a maximum yield of 85.85%. XRD and FTIR analyses were used to assess the physicochemical characteristics of the extracted silica. The aqueous solutions of methyl orange were used to test the adsorption efficiency of silica. The percent of removal efficiency for methyl orange was 90.48%.

Removal of color from pulp and paper mill wastewater- methods and techniques- A review

The pulp and paper industry consumes a huge amount of water and releases more polluted and colored wastewater every year. Many conventional techniques are used in the treatment of paper industry wastewater. However, for color removal from paper mill effluent, there is no proven method so far, on an industrial scale. Due to high energy input and high cost, there is an urgent need to find out a new technique that must be sustainable, economical, and environment friendly. Various methods have been investigated on bench scale and pilot scale also but no proven method for color removal on an industrial scale. The paper provides an overview of the color removal techniques from different sources of pulp and paper mill wastewater discharged by various industries. The review described various components involved in various processes for color removal from paper mill waste water. The present works focus on processes like chemical, chemical/physical, biological, physicochemical, and electrochemical applied in color removal from paper mill wastewater. The present review gives key information on the effectiveness, use, betterment, and limitations of numerous methods of treatment targeted at color removal from paper mill wastewater using various techniques still under evolution.

Phosphorus and sulphates removal from wastewater using copper smelter slag washed with acid

Abstract

In this study, we present the performance of acid washed copper smelter slag for the adsorption of phosphates and sulphates from wastewater. The aim of the study was to investigate the removal of phosphates and sulphates from wastewater using acid washed copper smelter slag at batch scale by exploring influences of different variables. The leachate concentrations of copper, iron, manganese and lead released from the adsorbent were 1.8, 128.2, 0.32 and 0.20 mg L−1, respectively at pH 2. The point of zero charge was at pH 6.04, Pseudo-Second Order kinetic model described the adsorption process better with an R2 value of 0.99. The experimental maximum adsorption capacities for phosphates and sulphates were 0.51 and 0.24 mg g−1 media, respectively, and 0.96 mg P g−1 media at pH 12 and 0.39 mg g−1 media for sulphates at pH 2, respectively. The process was endothermic with temperature having insignificant impact during adsorption. The maximum adsorption capacities for thermodynamic study were 0.103 ± 0.09 and 0.046 ± 0.004 mg g−1 media respectively, for PO43− P and SO42− at 60 °C. This study showed that acid washed copper smelter slag has an improved adsorption capacity for phosphate and sulphate ions but further investigations should be conducted to find ways of further improving the adsorbent performance.

Article highlights

Meso- and macroporous silica-based arsenic adsorbents: effect of pore size, nature of the active phase, and silicon release

Arsenic pollution in ground and drinking water is a major problem worldwide due to the natural abundance of arsenic by dissolution from ground sediment or mining activities from anthropogenic activities. To overcome this issue, iron oxides as low-cost and non-toxic materials, have been widely studied as efficient adsorbents for arsenic removal, including when dispersed within porous silica supports. In this study, two head-to-head comparisons were developed to highlight the As(v)-adsorptive ability of meso- and macrostructured silica-based adsorbents. First, the role of the textural properties of a meso-(SBA15) and macrostructured (MOSF) silica support in affecting the structural-morphological features and the adsorption capacity of the active phase (Fe2O3) have been studied. Secondly, a comparison of the arsenic removal ability of inorganic (Fe2O3) and organic (amino groups) active phases was carried out on SBA15. Finally, since silica supports are commonly proposed for both environmental and biomedical applications as active phase carriers, we have investigated secondary silicon and iron pollution. The batch tests at different pH revealed better performance from both Fe2O3-composites at pH 3. The values of q m of 7.9 mg g-1 (53 mg gact -1) and 5.5 mg g-1 (37 mg gact -1) were obtained for SBA15 and MOSF, respectively (gact stands for mass of the active phase). The results suggest that mesostructured materials are more suitable for dispersing active phases as adsorbents for water treatment, due to the obtainment of very small Fe2O3 NPs (about 5 nm). Besides studying the influence of the pore size of SBA15 and MOSF on the adsorption process, the impact of the functionalization was analyzed on SBA15 as the most promising sample for As(v)-removal. The amino-functionalized SBA15 adsorbent (3-aminopropyltriethoxysilane, APTES) exhibited a q m of 12.4 mg g-1 and faster kinetics. Furthermore, issues associated with the release of iron and silicon during the sorption process, causing secondary pollution, were evaluated and critically discussed.

Rhizosphere Bacteria in Plant Growth Promotion, Biocontrol, and Bioremediation of Contaminated Sites: A Comprehensive Review of Effects and Mechanisms

Agriculture in the 21st century is facing multiple challenges, such as those related to soil fertility, climatic fluctuations, environmental degradation, urbanization, and the increase in food demand for the increasing world population. In the meanwhile, the scientific community is facing key challenges in increasing crop production from the existing land base. In this regard, traditional farming has witnessed enhanced per acre crop yields due to irregular and injudicious use of agrochemicals, including pesticides and synthetic fertilizers, but at a substantial environmental cost. Another major concern in modern agriculture is that crop pests are developing pesticide resistance. Therefore, the future of sustainable crop production requires the use of alternative strategies that can enhance crop yields in an environmentally sound manner. The application of rhizobacteria, specifically, plant growth-promoting rhizobacteria (PGPR), as an alternative to chemical pesticides has gained much attention from the scientific community. These rhizobacteria harbor a number of mechanisms through which they promote plant growth, control plant pests, and induce resistance to various abiotic stresses. This review presents a comprehensive overview of the mechanisms of rhizobacteria involved in plant growth promotion, biocontrol of pests, and bioremediation of contaminated soils. It also focuses on the effects of PGPR inoculation on plant growth survival under environmental stress. Furthermore, the pros and cons of rhizobacterial application along with future directions for the sustainable use of rhizobacteria in agriculture are discussed in depth.