Microbial and plant derived biomass for removal of heavy metals from wastewater

Metal-tolerant morganella morganii isolates can potentially mediate nickel stress tolerance in Arabidopsis by upregulating antioxidative enzyme activities

Plant growth-promoting rhizobacteria (PGPRs) have been utilized to immobilize heavy metals, limiting their translocation in metal contaminated settings. However, studies on the mechanisms and interactions that elucidate how PGPRs mediate Nickel (Ni) tolerance in plants are rare. Thus, in this study we investigated how two pre-characterized heavy metal tolerant isolates of Morganella morganii (ABT9 and ABT3) improve Ni stress tolerance in Arabidopsis while enhancing its growth and yield. Arabidopsis seedlings were grown for five weeks in control/Ni contaminated (control, 1.5 mM and 2.5 mM) potted soil, in the presence or absence of PGPRs. Plant growth characteristics, quantum yield, and antioxidative enzymatic activities were analyzed to assess the influence of PGPRs on plant physiology. Oxidative stress tolerance was quantified by measuring MDA accumulation in Arabidopsis plants. As expected, Ni stress substantially reduced plant growth (shoot and root fresh weight by 53.25% and 58.77%, dry weight by 49.80% and 57.41% and length by 47.16% and 64.63% over control), chlorophyll content and quantum yield (by 40.21% and 54.37% over control). It also increased MDA content by 84.28% at higher (2.5 mM) Ni concentrations. In contrast, inoculation with M. morganii led to significant improvements in leaf chlorophyll, quantum yield, and Arabidopsis biomass production. The mitigation of adverse effects of Ni stress on biomass observed in M. morganii-inoculated plants was attributed to the enhancement of antioxidative enzyme activities compared to Ni-treated plants. This upregulation of the antioxidative defense mechanism mitigated Ni-induced oxidative stress, leading to improved performance of the photosynthetic machinery, which, in turn, enhanced chlorophyll content and quantum yield. Understanding the underlying mechanisms of these tolerance-inducing processes will help to complete the picture of PGPRs-mediated defense signaling. Thus, it suggests that M. morganii PGPRs candidate can potentially be utilized for plant growth promotion by reducing oxidative stress via upregulating antioxidant defense systems in Ni-contaminated soils and reducing Ni metal uptake.

Tannery effluent treatments with mangrove fungi, grass root biomass, and biochar

Tannery effluents contain high amounts of polluting chemicals, such as salts and heavy metals released often to surface waters. New economic and eco-friendly purification methods are needed. Two adsorbing materials and five salt-tolerant fungal isolates from mangrove habitat were studied. Purification experiments were carried out using the pollutant adsorbents biochar and the biomass of vetiver grass (Chrysopogon zizanioides) roots and the fungi Cladosporium cladosporioides, Phomopsis glabrae, Aspergillus niger, Emericellopsis sp., and Scopulariopsis sp., which were isolated from mangrove sediment. They efficacy to reduce pollutants was studied in different combinations. Salinity, turbidity, total dissolved solids, total suspended solids, phenols, nitrogen, ammonia. Biological and chemical oxygen demand (BOD, COD) and several heavy metals were measured. The adsorbents were efficient reducing the pollutants to 15-50% of the original. The efficiency of the combination of biochar and roots was generally at the same level as the adsorbents alone. Some pollutants such as turbidity, COD and ammonium were reduced slightly more by the combination than the adsorbents alone. From all 14 treatments, Emericellopsis sp. with biochar and roots appeared to be the most efficient reducing pollutants to < 10-30%. BOD and COD were reduced to ca 5% of the original. The treatment was efficient in reducing also heavy metals (As, Cd, Cr, Mn Pb, Zn). The fungal species originating from the environment instead of the strains present in the tannery effluent reduced pollutants remarkably and the adsorbents improved the reduction efficiency. However, the method needs development for effluents with high pollutant concentrations to fulfil the environmental regulations.

Exploring the effective adsorption of polystyrene microplastics from aqueous solution with magnetically separable nickel/reduced graphene oxide (Ni/rGO) nanocomposite

Microplastics (MPs) are a potential threat to both humans and aquatic environment as they serve as carriers of various contaminants necessitating the development of reliable, efficient, and ecofriendly techniques to remove MPs from water. In this study, reduced graphene oxide (rGO) magnetized using nickel nanoparticles was utilized as a potent adsorbent for the effective removal of microplastics from water. The synthesized nickel/reduced graphene oxide (Ni/rGO) nanocomposite was characterized by X-ray diffraction (XRD), Raman spectra, vibrating sample magnetometer (VSM), scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDX), thermogravimetric analysis, and Brunauer-Emmett Teller (BET) analysis. Magnetic Ni/rGO nanocomposite exhibited significant adsorption capability for polystyrene (PS) microspheres allowing the formation of PS-Ni/rGO complex which can be easily separated out using a magnet. The SEM images of PS-Ni/rGO complex confirmed the adsorption of PS microspheres onto the nano adsorbent due to hydrophobic interaction. The adsorbent demonstrated a maximum adsorption capacity of 1250 mg/g. The analysis of isotherm and kinetic models demonstrated that the adsorption mechanism conformed to the Langmuir isotherm and followed pseudo second order kinetics. This study paves a new pathway for the application of magnetically modified reduced graphene oxide for the expedient removal of microplastics from water with the ease of separation using a magnet. The adsorbent was recycled and reused for three times.

Toxicity and bioremediation of the lead: a critical review

Lead is a naturally occurring, bluish-gray metal that is found in small quantities in the earth's crust. The existing literature demonstrates that non-biodegradable character and continuous use results in accumulation of lead concentration in the environment and causes various ill effects such as neurotoxicity, change in psychological and behavioral development of different organisms. Nowadays the most effective technique in the revival of the environment is bioremediation and it is environmentally friendly and cost-effective. Bacterial strains such as Oceanobacillus profundus and Lactobacillus acidophilus ATCC4356 have the ability to reduce lead 97% and 73.9%, respectively. Similarly some species of algae and fungal strains also showed lead removal efficiency as 74% (spirulina), 97.1% (Chlorella kessleri), 95.5% (Penicillium janthinillum) and 86% (Aspergillus flavus). Biodegradation of lead by various microbes would be the most efficient and sustainable approach. This review focuses on toxicity, fate of lead in the environment and its microbial degradation.

Isolation of chromium resistant bacteria from tannery waste and assessment of their chromium reducing capabilities - A Bioremediation Approach

Every year different industries generate numerous toxic environmental polluting agents throughout the world. Among the polluting agents, chromium (Cr) toxicity is a great concern nowadays. It is continuously released in soil and water, causing environmental and health problems thereby raising several public health issues in developing countries like Bangladesh. The primary goal of this study was to provide a bioremediation option to reduce toxic hexavalent chromium to a less toxic trivalent form by isolating chromium resistant bacteria from Cr contaminated environments. Bacterial isolates were obtained from seven tannery waste samples collected from Hazaribag and Hemayetpur, Savar, Dhaka. Twenty morphologically distinct colonies were screened, of which six showed the highest resistance. These were designated as A1, A2, B1, F1, K1, and P1. Their maximum tolerance to Cr (VI) was determined through growth assays in varying chromium concentrations up to 8000 mg/L on LB agar media. Strains A2 and B1 exhibited the highest resistances to chromium at 7700 mg/L and 7200 mg/L respectively. Bacterial strains A2 and B1 were identified through several biochemical tests and after PCR analysis finally identified as Bacillus sp. and Micrococcus sp. respectively. Their Cr (VI) reduction capabilities were assessed quantitatively using the diphenylcarbazide colorimetric assay. Both strains exhibit approximately 100% reduction of chromium from 100 mg/L concentration to non-toxic form within 48 h using accurate analytical methods. This study demonstrates the isolation of highly chromium-resistant bacteria from tannery waste that can efficiently bioremediate Cr (VI) pollution, thus providing an eco-friendly and cost-effective bioremediation approach.

Design and application of metal organic frameworks for heavy metals adsorption in water: a review

The growing apprehension surrounding heavy metal pollution in both environmental and industrial contexts has spurred extensive research into adsorption materials aimed at efficient remediation. Among these materials, Metal-Organic Frameworks (MOFs) have risen as versatile and promising contenders due to their adjustable properties, expansive surface areas, and sustainable characteristics, compared to traditional options like activated carbon and zeolites. This exhaustive review delves into the synthesis techniques, structural diversity, and adsorption capabilities of MOFs for the effective removal of heavy metals. The article explores the evolution of MOF design and fabrication methods, highlighting pivotal parameters influencing their adsorption performance, such as pore size, surface area, and the presence of functional groups. In this perspective review, a thorough analysis of various MOFs is presented, emphasizing the crucial role of ligands and metal nodes in adapting MOF properties for heavy metal removal. Moreover, the review delves into recent advancements in MOF-based composites and hybrid materials, shedding light on their heightened adsorption capacities, recyclability, and potential for regeneration. Challenges for optimization, regeneration efficiency and minimizing costs for large-scale applications are discussed.

Molasses-based in situ bio-sequestration of Cr(VI) in groundwater under flow condition

The in situ biosequestration of Cr(VI) in groundwater with molasses as the carbon source was studied based on column experiments and model simulation in this study. Compared with biological reduction, molasses-based chemical reduction did not cause significant Cr(VI) removal at molasses concentration as high as 1.14 g L-1. The molasses at a concentration as low as 0.57 g L-1 could support biofilm-based Cr(VI) sequestration under flow conditions and showed better sequestration performances than D-glucose and emulsified vegetable oil (8 g L-1). The existence of molasses (1.14 g L-1) decreased the pH of the effluent from 7.5 to 6.3 and the oxidation-reduction potential from 275 mV to 220 mV in the groundwater, which was responsible for reduction and thus the sequestration of Cr(VI). Advection-dispersion-reaction model well described the process of the Cr(VI) transport with biosequestration in the column (R2 ≥ 0.96). Owing to the Cr(VI) toxicity to the biofilms, the removal ratio decreased by 24% with a rise of Cr(VI) concentration from 8.6 to 43 mg L-1. The prolongation of hydraulic retention time could promote the performance of Cr(VI) biosequestration. The chemical form of Cr deposited as the product of bio-reduction was confirmed as Cr(OH)3·H2O and other complexes of Cr(III). Our work demonstrated the efficacy of molasses for in situ sequestration of Cr(VI) under the dynamic flow condition and provide some useful information for Cr-contaminated groundwater remediation.

Pyrrhotite-dependent microbial reduction and magnetic separation for efficient vanadium detoxification and recovery in contaminated aquifer

Microbial reduction under anaerobic condition is a promising method for remediating vanadate [V(V)] contamination in aquifers, while V(V) may be re-generated with redox fluctuations. The inability to remove vanadium after remediation has become a key issue limiting bioremediation. In this study, we proposed the use of pyrrhotite, a natural mineral with magnetic properties, to immobilize V(V) to insoluble V(IV) under microbial action and remove vanadium from the aquifer using a magnetic field, which could avoid the problem of V(V) recontamination under redox fluctuating conditions. Up to 49.0 ± 4.7 % of vanadium could be removed from the aquifer by the applied magnetic field, and the vanadium in the aquifer after the reaction was mainly in the acid-extractable and reducible states. pH had a strong effect on the magnetic recovery of V(V), while the influence of initial V(V) concentration was weak. Microbial community structure analysis showed that Thiobacillus, Proteiniphilum, Fermentimonas, and Desulfurivibrio played key roles for V(V) reduction and pyrrhotite oxidation. Structural equation model indicated the positive correlation between these genera with the magnetic recovery of vanadium. Real time-qPCR confirmed the roles of functional genes of V(V) reduction (napA and nirK) and SO42- reduction (dsrA) in such biological processes. This study provides a novel route to sustainable V(V) remediation in aquifers, with synchronous recovery of vanadium resources without rebound.

Ion-imprinted chitosan prepared without cross-linking agent for efficient selective adsorption of Al(III) from rare earth solution

In the aqueous phase, ion-imprinted materials exhibit excellent selective adsorption properties for specific ions, but their complicated preparation process and large amount of crosslinker consumption limit their application. In this study, ion-imprinted chitosan (IIP-CS) was prepared by a simple one-step hydrothermal method without a cross-linking agent for the efficient adsorption of trace amounts of Al(III) from a rare earth solution. The structures and morphology of IIP-CS were analyzed by FT-IR, SEM, and XRD. The Al(III) adsorption characteristics of IIP-CS were investigated under various preparation processes and adsorption conditions. It was found that the optimum mass ratio of IIP-CS is 3 : 1 and pH is 3 and the adsorption capacity reaches up to 40.36 mg g-1. In addition, three different isothermal models-Temkin, Freundlich, and Langmuir-were used to analyze the equilibrium adsorption of IIP-CS in aqueous solution. The results obtained are consistent with the Langmuir model. The adsorption process of Al(III) on IIP-CS follows a pseudo-secondary kinetic model, suggesting that electron sharing or exchange between IIP-CS and Al(III) is a key factor affecting its adsorption rate. IIP-CS shows high selectivity coefficients for Al(III) in mixtures of La(III), Y(III), and Gd(III), which are 792.50, 163.26, and 55.16, respectively. The mechanism of action is the formation of a complex via amidation between Al(III) and IIP-CS. IIP-CS is an adsorbent with excellent regeneration and selective adsorption performance in aqueous solution.

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.

Adsorptive removal of heavy metals from wastewater using Cobalt-diphenylamine (Co-DPA) complex

Heavy metals like Cadmium, Lead, and Chromium are the pollutants emitted into the environment through industrial development. In this work, a new diphenylamine coordinated cobalt complex (Co-DPA) has been synthesized and tested for its efficiency in removing heavy metals from wastewater, and its adsorption capacity was investigated. The effectiveness of heavy metals removal by Co-DPA was evaluated by adjusting the adsorption parameters, such as adsorbent dose, pH, initial metals concentration, and adsorption period. Heavy metal concentrations in real sample were 0.267, 0.075, and 0.125 mg/L for Cd2+, Pb2+, and Cr3+ before using as-synthesized Co-DPA to treat wastewater. After being treated with synthesized Co-DPA the concentration of heavy metals was reduced to 0.0129, 0.00028, 0.00054 mg/L for Cd2+, Pb2+, and Cr3+, respectively, in 80 min. The removal efficiency was 95.6%, 99.5%, and 99.5% for the respective metals. The adsorption process fitted satisfactorily with Freundlich isotherm with R2(0.999, 0.997, 0.995) for Cd2+, Pb2+, and Cr3+, respectively. The kinetic data obeyed the pseudo-second order for Cd2+ and Cr2+ and the pseudo-first order for Pb2+. Based on the results obtained within the framework of this study, it is concluded that the as-synthesized Co-DPA is a good adsorbent to eliminate heavy metal ions like Cd2+, Pb2+, and Cr3+from wastewater solution. In general, Co-DPA is a promising new material for the removal of heavy metal ions from water.

A novel approach to modify Stenotrophomonas sp. D6 by regulating the salt composition in the growth medium: Enhanced removal performance of Cr(VI)

In this study, a novel and effective modified microbial reducing agent was developed to detoxify Cr(VI) from aqueous solutions. This was achieved by carefully controlling specific salt components in the growth medium. Based on the single-salt modification, several effective modified salts were selected and added to the medium for synergistic modification. The results showed that the synergistic modification with NH4Cl and KH2PO4 had the best detoxification effect on Cr(VI), reaching 98.5% at 100 mg/L Cr(VI), which was much higher than the 43.7% of the control (original Luria-Bertani medium). This enhancement was ascribed to the ability of NH4Cl and KH2PO4 to stimulate the growth of Stenotrophomonas sp. D6 promoted chromate reductase secretion. The protein content of the modified medium supernatant was significantly increased by 10.76% compared to that before modification. Based on the micro-characterization, the main process for the elimination of Cr(VI) is microbial reduction rather than biosorption. Most of the reduced Cr was found in the extracellular suspension, thereby suggesting that the primary reduction occurred outside the cells, whereas only a small fraction was detected intracellularly. Overall, this study provides a simple and effective method for microbial treatment of heavy metals in aqueous solutions.

Life cycle assessment of integrated microalgae oil production in Bojongsoang Wastewater Treatment Plant, Indonesia

This study aims to determine the eco-friendliness of microalgae-based renewable energy production in several scenarios based on life cycle assessment (LCA). The LCA provides critical data for sustainable decision-making and energy requirement analysis, including net energy ratio (NER) and cumulative energy demand (CED). The Centrum voor Milieuwetenschappen Leiden (CML) IA-Baseline was used on environmental impact assessment method by SimaPro v9.3.0.3® software and energy analysis of biofuel production using native polyculture microalgae biomass in municipal wastewater treatment plants (WWTP) Bojongsoang, Bandung, Indonesia. The study was analyzed under three scenarios: (1) the current scenario; (2) the algae scenario without waste heat and carbon dioxide (CO2); and (3) the algae scenario with waste heat and carbon dioxide (CO2). Waste heat and CO2 were obtained from an industrial zone near the WWTP. The results disclosed that the microalgae scenario with waste heat and CO2 utilization is the most promising scenario with the lowest environmental impact (- 0.139 kg CO2eq/MJ), positive energy balance of 1.23 MJ/m3 wastewater (NER > 1), and lower CED value across various impact categories. It indicates that utilizing the waste heat and CO2 has a positive impact on energy efficiency. Based on the environmental impact, NER and CED values, this study suggests that the microalgae scenario with waste heat and CO2 is more feasible and sustainable to adopt and could be implemented at the Bojongsoang WWTP.

Effect of amino acids on biomineralization of lead ions by Aspergillus niger

This study investigates the biomineralization of lead ions by Aspergillus niger from aqueous environments, focusing on the dynamic effects of fungal metabolism and biological components. Three biomolecules (glutamate, methionine, and lysine) were used to induce lead oxalate mineralization under lead stress. Comparative experiments were conducted to analyze the growth characteristics and Pb (II) removal ability of A. niger, as well as the morphological and structural properties of the resulting lead oxalate minerals using inductively coupled plasma atomic emission spectroscopy, X-ray powder diffraction, and scanning electron microscopy-energy dispersive spectroscopy techniques. The findings reveal that A. niger plays a crucial role in controlling the mineralization process of Pb (II), with biomineralization experiments demonstrating the specific morphogenesis of lead oxalate over time. Additionally, the inclusion of the three biomolecules in the system indirectly influenced the rate of Pb (II) removal and mineral morphology. These results contribute to a better understanding of A. niger-mediated biomineralization process of lead oxalate and suggest its potential application in the removal of Pb (II) from aqueous environments, particularly in combination with amino acids for enhanced immobilization and mineral recovery. PRACTITIONER POINTS: Fungal activity and amino acids play a crucial role in shaping lead oxalate crystals during water treatment processes. Specific amino acids can effectively delay lead oxalate recrystallization, enhancing the stability and removal efficiency of the crystals. Biomineralization mediated by fungi offers a promising and eco-friendly approach for lead removal and recovery in wastewater treatment. Exploring the influence of organic additives and fungal metabolism on crystal growth provides valuable insights for developing efficient remediation strategies. Further research on the utilization of fungi and amino acids can help with innovative and sustainable wastewater treatment technologies.

Heavy metals concentration in zooplankton (copepods) in the western Bay of Bengal

Along the coastline, urbanisation and industrialization pose significant challenges to marine habitats and biodiversity. Most wastewater that reaches the marine environment contains toxic metals, which, as they are non-biodegradable, accumulate in the biota and enter the marine food chain. This study presents the concentration of nine heavy metals (Fe, Zn, Cu, Co, Cr, Mn, Ni, Pb, and Cd) in zooplankton (copepods) during the Spring Intermonsoon/Pre-Monsoon (April 2019) in the western Bay of Bengal (BoB). Higher Fe concentrations were found in copepods both nearshore (42,352 µg/g) and offshore (9835 µg/g). However, the relative amounts of heavy metals in copepods from 16 locations (eight nearshore and eight offshore) varied in the order of Fe > Zn > Cu > Co > Cr > Mn > Ni > Pb > Cd. The copepods in the nearshore locations had higher concentrations of heavy metals than those offshore. Compared to earlier data on heavy metals, particularly those that are physiologically non-essential and toxic, the current study demonstrates higher amounts of these metals in copepods in the inshore BoB [Ni (avg. 58.7 ± 5.5 µg/g), Pb (avg. 25.6 ± 4.7 µg/g), and Cd (avg. 16.4 ± 0.9 µg/g)]. Considering the strong East India Coastal Currents in the western BoB, trace metal-concentrated copepods could be transported too far along the Indian coastline from the current study area.

Evaluation of metal pollution related to human health risk in freshwater snail Viviparus contectus (Millet, 1813) as a potential bioindicator species in Lake Habitat (Turkey)

Freshwater mollusks are employed as bioindicators for the assessment of water quality in biomonitoring studies since the water quality of natural resources is crucial for humans. The freshwater snail species known as Viviparus contectus (Viviparidae: Gastropoda) is one that people eat. Here, the levels of heavy metals (Cd, Cr, Pb, As, Zn, and Cu) in water and V. contectus samples were determined. An Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES, Spectro Arcos, vertical plasma) was used for the analysing the heavy metal concentrations in water and freshwater snail samples. The results of the current investigation demonstrated that freshwater snails accumulated metals in their water and soft tissues in the following orders: Pb > Cr = Zn = Cu = Cd = As and Zn > Cu > Pb > Cd > As = Cr. Autumn was the time of year when higher amounts of heavy metals (As, Cr, Cu, Zn, and Hg) were found. Pb content in the freshwater snail samples was strongly impacted by seasonal fluctuations (P 0.05). For adults, the EDI (estimated daily intake) values were lower than the TDI (tolerable daily intake) values, and the HI (hazard index) values were below 1. Freshwater snail samples had Zn and Pb levels that were over the FAO/WHO, Turkish Food Codex, JECFA, and EC limit values. Except for Pb, the water study shows mean metal concentrations below the USEPA, Turkish Pollution Control Regulation, and World Health Organisation maximum allowed levels. Aquatic ecosystems were negatively impacted by anthropogenic activities overall, and this study can provide a helpful data set for investigations on metallic contamination in water bodies and biomonitoring in freshwater ecosystems.

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.

Banana Peel Powder Biosorbent for Removal of Hazardous Organic Pollutants from Wastewater

Disposing of pollutants in water sources poses risks to human health and the environment, but biosorption has emerged as an eco-friendly, cost-effective, and green alternative for wastewater treatment. This work shows the ability of banana peel powder (BPP) biosorbents for efficient sorption of methylene blue (MB), atrazine, and glyphosate pollutants. The biosorbent highlights several surface chemical functional groups and morphologies containing agglomerated microsized particles and microporous structures. BPP showed a 66% elimination of MB in 60 min, with an adsorption capacity (qe) of ~33 mg g-1, and a combination of film diffusion and chemisorption governed the sorption process. The biosorbent removed 91% and 97% of atrazine and glyphosate pesticides after 120 min, with qe of 3.26 and 3.02 mg g-1, respectively. The glyphosate and atrazine uptake best followed the Elovich and the pseudo-first-order kinetic, respectively, revealing different sorption mechanisms. Our results suggest that BPP is a low-cost biomaterial for green and environmentally friendly wastewater treatment.

Biological approaches for E-waste management: A green-go to boost circular economy

E-waste is a pressing situation on human due to its complex composition. Although E-waste on one hand has some toxic components but at the same time, it would be a promising business sector. Recycling of E-waste to mine-out valuable metals and other components has opened a chance of business and hence a way towards transformation of linear economy to circular one. Chemical, physical and traditional technologies are holding the position in E-waste recycling sector but sustainability with respect to cost and environmental issues is a major concern associated with these technologies. In order to overcome these gaps, lucrative, environment friendly and sustainable technologies need to be implied. Biological approaches could be a green and clean approach to handle E-waste through sustainable and cost-effective means by considering socio-economic and environmental aspects. This review elaborates biological approaches for E-waste management and advancements in expanse. The novelty covers the environmental and socio-economic impacts of E-waste, solution and further scope of biological approaches, further research and development need in this contour to come up with sustainable recycling process.

Assessment and characterization of heavy metals resistance bacteria isolated in Southwestern Mediterranean coastal waters (Bou-Ismail Bay): Impacts of anthropogenic activities

Bacteria present in the marine environment can cause ecological risks and seriously impact human health through direct contact or the food chain. This paper examines bacterial resistance to heavy metals and anthropogenic inputs' influence in four Bou-Ismail Bay regions (Algerian coast). The study was conducted from May to October 2018. High levels of resistance of total flora and total coliform were observed respectively for zinc (29.5 %, 30.5 %), copper (26.2 %, 20.7 %), mercury (17.4 %, 17.2 %), lead (16.9 %, 14.2 %), and cadmium (8.9 %, 0 %). A total 118 metal resistant bacteria were identified. All isolates were tested against 5 heavy metals and 7 antibiotics. The isolates showed tolerance to different concentrations of heavy metals ranging from 12.5 to 6400 μg/ml and exposed a co-resistance to the other heavy metals. The majority of strains were multi-resistant to heavy metals and antibiotics. Therefore, the bacteria isolated from Bou-Ismail Bay are highly resistant to heavy metals and antibiotics.

Bioaccumulation and Bioremediation of Heavy Metals in Fishes-A Review

Heavy metals, the most potent contaminants of the environment, are discharged into the aquatic ecosystems through the effluents of several industries, resulting in serious aquatic pollution. This type of severe heavy metal contamination in aquaculture systems has attracted great attention throughout the world. These toxic heavy metals are transmitted into the food chain through their bioaccumulation in different tissues of aquatic species and have aroused serious public health concerns. Heavy metal toxicity negatively affects the growth, reproduction, and physiology of fish, which is threatening the sustainable development of the aquaculture sector. Recently, several techniques, such as adsorption, physio-biochemical, molecular, and phytoremediation mechanisms have been successfully applied to reduce the toxicants in the environment. Microorganisms, especially several bacterial species, play a key role in this bioremediation process. In this context, the present review summarizes the bioaccumulation of different heavy metals into fishes, their toxic effects, and possible bioremediation techniques to protect the fishes from heavy metal contamination. Additionally, this paper discusses existing strategies to bioremediate heavy metals from aquatic ecosystems and the scope of genetic and molecular approaches for the effective bioremediation of heavy metals.

A Mathematical Study of Metal Biosorption on Algal-Bacterial Granular Biofilms

A multiscale mathematical model describing the metals biosorption on algal-bacterial photogranules within a sequencing batch reactor (SBR) is presented. The model is based on systems of partial differential equations (PDEs) derived from mass conservation principles on a spherical free boundary domain with radial symmetry. Hyperbolic PDEs account for the dynamics of sessile species and their free sorption sites, where metals are adsorbed. Parabolic PDEs govern the diffusion, conversion and adsorption of nutrients and metals. The dual effect of metals on photogranule ecology is also modelled: metal stimulates the production of EPS by sessile species and negatively affects the metabolic activities of microbial species. Accordingly, a stimulation term for EPS production and an inhibition term for metal are included in all microbial kinetics. The formation and evolution of the granule domain are governed by an ordinary differential equation with a vanishing initial value, accounting for microbial growth, attachment and detachment phenomena. The model is completed with systems of impulsive differential equations describing the evolution of dissolved substrates, metals, and planktonic and detached biomasses within the granular-based SBR. The model is integrated numerically to examine the role of the microbial species and EPS in the adsorption process, and the effect of metal concentration and adsorption properties of biofilm components on the metal removal. Numerical results show an accurate description of the photogranules evolution and ecology and confirm the applicability of algal-bacterial photogranule technology for metal-rich wastewater treatment.

Current progress of continuous-flow aerobic granular sludge: A critical review

Aerobic granular sludge (AGS) is promising for water resource recovery. Despite the mature granulation strategies in sequencing batch reactor (SBR), the application of AGS-SBR in wastewater treatment is usually costly as it requires extensive infrastructure conversion (e.g., from continuous-flow reactor to SBR). In contrast, continuous-flow AGS (CAGS) that does not require such infrastructure conversion is a more cost-effective strategy to retrofit existing wastewater treatment plants (WWTPs). Formation of aerobic granules in both batch and continuous-flow mode depends on many factors, including selection pressure, feast/famine conditions, extracellular polymeric substances (EPS), and environmental conditions. Compared with AGS in SBR, creating proper conditions to facilitate granulation in continuous-flow mode is challenging. Researchers have been seeking to tackle this bottleneck by studying the impacts of selection pressure, feast/famine conditions, and operating parameters on granulation and granule stability in CAGS. This review paper summarizes the state-of-the-art knowledge regarding CAGS for wastewater treatment. Firstly, we discuss the CAGS granulation process and effective parameters (i.e., selection pressure, feast/famine conditions, hydrodynamic shear force, reactor configuration, the role of EPS, and other operating factors). Then, we evaluate CAGS performance in removing COD, nitrogen, phosphorus, emerging pollutants, and heavy metals from wastewater. Finally, the applicability of the hybrid CAGS systems is presented. At last, we suggest that integrating CAGS with other treatment methods such as membrane bioreactor (MBR) or advanced oxidation processes (AOP) can benefit the performance and stability of granules. However, future research should address unknowns including the relationship between feast/famine ratio and stability of the granules, the effectiveness of applying particle size-based selection pressure, and the CAGS performance at low temperatures.

Efficient Removal of Pb(Ⅱ) by Highly Porous Polymeric Sponges Self-Assembled from a Poly(Amic Acid)

Lead (II) (Pb(II)) is widespread in water and very harmful to creatures, and the efficient removal of it is still challenging. Therefore, we prepared a novel sponge-like polymer-based absorbent (poly(amic acid), PAA sponge) with a highly porous structure using a straightforward polymer self-assembly strategy for the efficient removal of Pb(II). In this study, the effects of the pH, dosage, adsorption time and concentration of Pb(II) on the adsorption behavior of the PAA sponge are investigated, revealing a rapid adsorption process with a removal efficiency up to 89.0% in 2 min. Based on the adsorption thermodynamics, the adsorption capacity increases with the concentration of Pb(II), reaching a maximum adsorption capacity of 609.7 mg g^-1 according to the Langmuir simulation fitting. Furthermore, the PAA sponge can be efficiently recycled and the removal efficiency of Pb(II) is still as high as 93% after five adsorption-desorption cycles. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses reveal that the efficient adsorption of Pb(II) by the PAA sponge is mainly due to the strong interaction between nitrogen-containing functional groups and Pb(II), and the coordination of oxygen atoms is also involved. Overall, we propose a polymer self-assembly strategy to easily prepare a PAA sponge for the efficient removal of Pb(II) from water.

Process parameters and biological mechanism of efficient removal of Cd(II) ion from wastewater by a novel Bacillus subtilis TR1

The safe treatment of heavy metals in wastewater is directly related to the human health and social development. In this paper, a new biological strain has been isolated from electroplating wastewater, which can effectively remove metal ions in wastewater. The results of 16 S rDNA sequencing analysis and NCBI GenBank database comparison show that the strain belongs to a novel Bacillus genus and names Bacillus subtilis TR1 with the accession number of OL441606. The removal rate of Cd(II) reaches to 85.68% with the conditions of pH = 7, C_0Cd(II) = 20 mg L^-1, t = 48 h, m = 0.1 g, and T = 35 °C. The biological removal mechanism of Cd(II) is in-depth studied by FTIR and XRD combined with third-generation sequencing. The results indicate that Bacillus subtilis TR1 removes Cd(II) mainly through two synergistic pathways, namely, extracellular chemisorption and intracellular bioaccumulation: 1) The groups carried on the surface of the strain, such as -COOH, -NH, -OH and C-H, have good chemisorption properties for Cd(II) and easily form cadmium containing chelation (-COO-Cd(II), -N-Cd(II), etc.) with these groups. The appearance of TR1 strain changes from cylindrical to spherical after Cd(II) adsorption, which is due to the biotoxicity of Cd(II); 2) Cd(II) exchanges on the surface of TR1 strain with K and Na ions released from the intracellular cytoplasm and enters the cytoplasm under the transfer of biological transport medium. This part of Cd(II) is converted into its own components by anabolic enzymes and accumulates in the cytoplasm. These data provide a new biological agent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge.

Removal of Copper Ions from Wastewater: A Review

Copper pollution of the world's water resources is becoming increasingly serious and poses a serious threat to human health and aquatic ecosystems. With reported copper concentrations in wastewater ranging from approximately 2.5 mg/L to 10,000 mg/L, a summary of remediation techniques for different contamination scenarios is essential. Therefore, it is important to develop low-cost, feasible, and sustainable wastewater removal technologies. Various methods for the removal of heavy metals from wastewater have been extensively studied in recent years. This paper reviews the current methods used to treat Cu(II)-containing wastewater and evaluates these technologies and their health effects. These technologies include membrane separation, ion exchange, chemical precipitation, electrochemistry, adsorption, and biotechnology. Thus, in this paper, we review the efforts and technological advances made so far in the pursuit of more efficient removal and recovery of Cu(II) from industrial wastewater and compare the advantages and disadvantages of each technology in terms of research prospects, technical bottlenecks, and application scenarios. Meanwhile, this study points out that achieving low health risk effluent through technology coupling is the focus of future research.

A review on algal biosorbents for heavy metal remediation with different adsorption isotherm models

Biosorbent composites like chitin, alginate, moss, xanthene, and cotton can be derived from biotic species such as plants, algae, fungi, and bacteria which can be used for the exclusion of both organic and inorganic toxicants from sewage, industrial effluent, polluted soils, and many more. The use of composites in place of raw substrates like alginate and chitin increases the adsorption capacity as CS₄CPL₁ beads increase the adsorption capacity for copper and nickel from 66.7 mg/g and 15.3 mg/g in the case of alginate microsphere to 719.38 mg/g and 466.07 mg/g respectively. Biosorbent fabricated from algae Chlorella vulgaris having surface area of 12.1 m²/g and pore size of 13.7 nm owing to which it displayed a higher adsorption capacity for Pb 0.433 mmol/g indicating their potential as an efficient biosorbent material. This article contains detailed information related to heavy metals as well as biosorbent that includes different isotherms, kinetics, techniques to estimate heavy metal concentration, removal methods, and adverse health effects caused due to heavy metal pollution. Apart from the above recovery and reuse of biosorbent, correlation with the sustainable development goals has also been included.

Radiation-Grafting on Polypropylene Copolymer Membranes for Using in Cadmium Adsorption

Graft copolymerization has been a popular technique in recent years for adding different functional groups to polymers. In our research, polypropylene (PP) films are grafted with acrylonitrile (An) and acrylic acid (AAc) monomers to make them hydrophilic while retaining their mechanical qualities. Gamma radiation is used in this approach to establish active spots on an inert polymer that are appropriate for adding monomers radicals to form grafts, a procedure that is extremely difficult to perform using normal chemical processes. The graft parameters are investigated in order to acquire the highest percentage of graft. FTIR (Fourier transform infrared spectroscopy) spectra are used to analyze the grafting of AAc and An. SEM (scanning electron microscopy) and XRD (X-ray diffraction) micrographs are used to validate them. The specimens' tensile strength and hardness are measured and contrasted with blank PP films. Measurements are made of the effects of grafting on the tensile strength and elongation of the films, and a crucial grafting degree is established in order to preserve these properties. Water uptake is measured to adapt the copolymer to water treatment, and thermal behavior TGA (thermal gravimetric analysis) and DSC (diffraction scanning calorimeter) of the produced copolymer were performed. The elimination of cadmium was verified by an atomic absorption spectrophotometer (AAS) under different conditions of pH, time, and degree of grafting.

Electron microscopic imaging and NanoSIMS investigation on physiological responses of Aspergillus niger under Pb(II) and Cd(II) stress

In the bioremediation process, coexistence of lead (Pb) and cadmium causes complex toxicity, resulting in the difficulty of bioremediation. This study investigated the physiological responses and bioaccumulation mechanisms of the typical filamentous fungus Aspergillus niger under the coexistence of Pb and Cd. Four treatments were set up, i.e., control, sole Pb, sole Cd, and coexistence of Pb and Cd. The morphology of A. niger were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Then, nano-scale secondary ion mass spectrometry (NanoSIMS) was applied to accurately investigate the distribution of heavy metals in the fungal cells under the coexistence of Pb and Cd. Finally, the metallogenic process and mineral types were simulated by Geochemist's Workbench (GWB). The electron microscopic and NanoSIMS imaging showed that Pb and Cd were accumulated in both the extracellular and intracellular regions of the A. niger cells. In particular, the accumulated Pb content was ten times higher than that of Cd. However, Cd showed stronger toxicity than Pb to A. niger. Compared with the control treatment, Cd stress resulted in a two-fold increase of cell diameter and more extracellular substances, whereas the cell diameter increased nearly four times in the coexistence treatment. Moreover, the bioaccumulation of Pb was more intense than that of Cd during competitive sorption. The GWB simulation confirmed that Pb²⁺ can form multiple minerals (e.g., PbC₂O₄, PbHPO₄, and Pb₃(PO₄)₂, etc.), which significantly weakened its toxicity on the cell surface. This study elucidated the morphological characteristics of A. niger and competitive bioaccumulation under the coexistence of Pb and Cd, which would facilitate the application of microorganisms to the bioremediation of coexisted metals.

Does the presence of heavy metal and catechol contaminants in organic waste challenge the physiological performance of the bioconverter Hermetia illucens?

The increased human activities and the worldwide population growth are constantly increasing the production of solid wastes. Over the years, waste management has thus become a prominent issue for several companies and municipalities, and several engineering techniques have been developed over the years in order to convert wastes into other solid materials or fuels. Yet, several techniques are important contributors to environmental pollution, and biological-based solutions have thus become progressively very popular. In particular, insect-based conversion of organic wastes represent eco-friendly tools, and the growth and development of insect species such as the black soldier fly have been tested and improved for a large diversity of organic wastes. However, organic wastes, including food wastes, may contain several pollutants such as heavy metals and catechol which could affect the bioconversion efficiency by incurring physiological costs that would be undetectable at the organismal level, i.e. have null to little effects on the life cycle of Hermetia illucens. In this context, assessments of antioxidant capacities can provide a rapid and low-cost evaluation of the capability of insects to handle exposure to heavy metals and catechol. Here, we aimed at measuring the physiological responses of the black soldier fly H. illucens grown on food wastes (kitchen, fruit or vegetable wastes) contaminated by cadmium, iron, lead or catechol. Biomarkers of oxidative stress (concentrations of hydrogen peroxide and protein carbonyls), non-enzymatic total antioxidant capacity (ascorbic acid amounts) and activity of enzymatic antioxidants (activities of superoxide dismutase and polyphenoloxidase) were measured from the gut of the larvae. We found no evidence of deleterious impacts of food waste contamination by catechol or heavy metals on H. illucens. In most experimental treatments, the array of physiological endpoints we measured for evaluating the degree of oxidative stress experienced by the larvae remained similar to controls. Possible physiological effects were reported for cadmium and catechol only, which tended to increase the oxidation of proteins and hydrogen peroxide in the larvae. Finally, our results suggested that the nature of the food waste could equally affect the physiological responses of the insect.

Synthesis and adsorption performance of three-dimensional gels assembled by carbon nanomaterials for heavy metal removal from water: A review

This review focuses on the removal of heavy metals from water by three-dimensional gels with carbon nanomaterials as the main building units. It highlights the fundamental knowledge, most recent advances, and future prospects of carbon nanomaterial-assembled gels (CNAGs) as effective adsorbents for heavy metals in water. Various synthesis methods of CNAGs including template-assisted, self-assembly and other methods are systematically summarized and evaluated. Adsorption performances of CNAGs to typical cationic and anionic heavy metals, especially lead, cadmium, mercury, chromium, and arsenic, are thoroughly examined and discussed in detail. These analyses bring out that composite CNAGs constructed from carbon nanomaterials with polymers or other engineered nanoparticles are the most promising adsorbents for heavy metal removal from water. Current challenges and future research directions that are critical to the applications of CNAGs in the removal of heavy metals from contaminated water are outlined at the end of the review.

Immobilization of exopolymeric substances from bacteria for metal removal: A study on characterization, optimization, reusability and toxicity

This study investigated the immobilization of exopolymeric substances (EPS) from Bacillus cereus using sodium alginate to form EPS beads for metal removal. The EPS beads were characterized and their optimum biosorption conditions established (biosorbent dosage, initial metal concentration and pH of metal solutions). The EPS beads were also tested for reusability by using them continuously for five metal removal cycles with desorption process in between cycles. The toxicity of the treated metal solutions was tested by phytotoxicity tests. Results revealed that EPS beads demonstrated significantly higher metal removal efficiency (Pb: 99.26%, Cr: 50.73%, Cu: 48.94%, Zn: 29.81%, Cd: 20.29%) compared to plain alginate beads (without EPS) (Pb: 84.45%, Cu: 31%, Cr: 28.37%, Zn: 11.91%, Cd: 9.37%). SEM-EDX analysis detected Cu, Pb, Zn, Cd and Cr on the surface of EPS beads. Optimum conditions for Pb removal by EPS beads were from the use of 0.1 g of biosorbent at 100 mg/L initial metal concentration and pH 5. By contrast, Cu, Zn, Cd and Cr were optimally removed by 0.3 g of biosorbent at 25 mg/L initial metal concentration and pH 5. EPS beads can be reused up to five times while maintaining a high rate of metal removal efficiency (Pb- 99.52%, Cr- 89.23%, Cu- 89.17%, Zn-52.52%, Cd-39.12%). This was achieved through desorption with nitric acid that consistently recovered 76-93% of the metal adsorbed. FTIR analysis reveals that nitric acid is capable of restoring the functional groups present within EPS beads, allowing it to bind with metal ions in repeated cycles. Metal solutions treated with EPS beads were less toxic as seedling shoots (pre-treated: 0-10 cm, post-treated: 1.2-18.1 cm) and roots (pre-treated: 0-7.8 cm, post-treated: 0.8-15.1 cm) grew well, which suggested that reduced levels of metals led to reduced phytotoxicity. This study provides an insight into the use of EPS beads for metal removal, highlighting the benefits and reusability of the beads for future wastewater treatment.

3D printed cylindrical capsules as a Chlorella pyrenoidosa immobilization device for removal of lead ions contamination

Immobilization is considered as a promising strategy toward the practical applications of powdered adsorbent. Herein, three dimensional (3D) printing cylindrical capsules with cross-linked PVA hydrogels membrane in encapsulate Chlorella pyrenoidosa (Cp) were utilized for removal of lead ions. The chemical compositions, hydrogels performance and morphologies of the membranes were determined by Fourier transformed infrared spectroscopy (FTIR), cross-linking degree, swelling degree, membrane flux and scanning electron microscopy (SEM). It is found that PVA cross-linking structure is successfully synthesized on the surface of capsule body and cap due to the presence of PVA in the filament. The lead ions adsorption capacity related to initial concentration of 50 mg/L in 48 h is reached 75.61%, revealing a good removal ability. The self-floating 3D printed capsules device also shows an excellent recovering property. After 7 runs of adsorption experiment, the lead ions adsorption ratio remains 78.56%, which will bring a broad prospect in wastewater treatment, chemical slow release along with sample preparation and separation.

Highly Selective Methodology for Entrapment and Subsequent Removal of Cobalt (II) Ions under Optimized Conditions by Micellar-Enhanced Ultrafiltration

Micellar-enhanced ultrafiltration (MEUF), being a separation technique, was used to remove cobalt metal ion (Co²⁺) from their aqueous solutions in an application to reduce the toxicity level from industrial effluents using a micellar solution of anionic and cationic surfactants. The metal ions were first adsorbed by using anionic surfactants, i.e., sodium dodecyl sulfate (SDS) and sodium oleate (SO). The calculations for partition (K_x) and binding constants (K_b) and their respective free energy of partition and binding (ΔG_p and ΔG_b kJmol^-1) helped significantly to find out the extent of binding or interaction of Co²⁺ with the surfactant and ΔG_p and ΔG_b were found to be -29.50 and -19.38 kJmol^-1 for SDS and -23.95 and -12.67 kJmol^-1 in the case of SO. MEUF work was also performed to find out the optimal conditions to remove metal pollutants from the aqueous system. For the said purpose, various factors and concentrations effect were studied, such as the concentration of the surfactant, concentration of the electrolyte (NaCl), transmembrane pressure, RPM, and pH. The efficiency of this process was checked by calculating various parameters, such as rejection percentage (R%) and permeate flux (J). A maximum rejection of 99.95% with SDS and 99.99% with SO was attained.

Separation of organic contaminant (dye) using the modified porous metal-organic framework (MIL)

Herein, the porous metal-organic framework (MIL-88B: Materials Institute Lavoisier) was synthesized and identified by FT-IR (Fourier transform infrared), SEM (Scanning Electron Microscopy), EDS (Energy Dispersive X-Ray Spectroscopy), and XRD (X-ray powder diffraction) analyses. Then MIL-88B was modified using 3-aminopropyl trimethoxy silane and presented as NH₂-MIL-88B. The synthesized materials were used to separate direct red dye 23 (DR23) as an organic contaminant from water. The effect of various important factors such as the amount of adsorbent, initial concentration of contaminants, and pH was investigated. The results showed that the modified adsorbent (NH₂-MIL-88B) had a higher adsorption capacity than the row adsorbent (MIL-88B). The amount of dye adsorption is high at lower pH values. The percentage of DR23 dye removal was complete under optimal conditions. Increasing the amount of adsorbent (0.001-0.003 g) and decreasing the pH (2.1-8.1) increases the percentage of dye removal and increasing the concentration of contaminant (50-125 mg/L) reduces the dye removal in the process. Isotherm data showed that the adsorption process followed the Langmuir model. Also, pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetic models were used to investigate the adsorption kinetics. Dye adsorption followed pseudo-second-order kinetics with correlation coefficient (0.99 <). The results showed that the modified adsorbent could be used as a suitable adsorbent with a high adsorption capacity for dye removal from water.

Arthrospira platensis as Bioremediator of Rhenium Mono- and Polymetallic Synthetic Effluents

Rhenium is a scarce and highly important metal for industry and technology. In the present study, the cyanobacterium Arthrospira platensis (Spirulina) was used to remove rhenium and related elements (Mo and Cu) from mono- and polymetallic synthetic effluents. Metal ions in different concentrations were added to the culture medium on the first, third, and fifth days of biomass growth, and their uptake by the biomass was traced using ICP-AES technique. The accumulation of rhenium in the biomass was dependent on the chemical composition of the effluents, and the highest uptake of 161 mg/kg was achieved in the Re-Cu system. The presence of rhenium, copper, and molybdenum affected the productivity of Spirulina biomass and its biochemical composition (proteins, carbohydrates, lipids, phycobiliproteins, the content of chlorophyll α and β-carotene). With the growth of biomass in the presence of rhenium or rhenium and molybdenum, a pronounced increase in productivity and protein content was observed. The presence of copper in systems has a negative effect on biomass productivity and biochemical composition. Arthrospira platensis may be of interest as a bioremediator of rhenium-containing effluents of various chemical compositions.

Removal of copper using chitosan beads embedded with amidoxime grafted graphene oxide nanohybids

This study explores a biopolymer-based composite system for metal decontamination of water using copper {Cu (II)} as a model pollutant. Novel composite beads of chitosan and amidoxime grafted graphene oxide (AOGO) were successfully prepared and used for the Cu (II) removal from aqueous solutions. For this purpose, acrylonitrile was first polymerized onto a gamma-irradiated and silanized graphene oxide substrate. The nitrile groups of polyacrylonitrile grafted graphene oxide (GO-g-PAN) were then chemically modified into amidoxime groups to form AOGO nanohybrids. These nanohybrids were mixed with a blend of chitosan (CS) and polyvinyl alcohol (PVA) and crosslinked using tetraethylorthosilicate (TEOS) to form composite CP/AOGO beads. Fourier transform infrared spectroscopy (FTIR) was used to study the structural changes at each step during the formation of composite beads. Scanning electron microscopic (SEM) analysis demonstrated that the beads had a well-developed spherical structure. The adsorption of Cu (II) onto CP/AOGO composite beads was studied under different conditions (initial concentration, pH, and contact time). The results revealed the potential of composite beads in copper removal from aqueous solutions.

Plant biomass as potential economic commodities for agricultural purposes

The world’s population is growing continually and is projected to reach nine billion by the year 2050. This growth rate requires increased and economically viable food production and an adequate supply of quality water to sustain life. Increased food production and supply of water require adding fertilizers and possible recycling of wastewater, to address the improvement of soils’ nutritional status and potable water shortages, respectively. The objectives of this work were to determine the nutrients in sewage-impacted wastewater, borehole water, agricultural waste, and commercial fertilizer (control) materials, and their heavy metal content was also carried out to determine their suitability for use. In addition, Moringa seed pods and Morula nutshells were investigated as a bioremedial approach for the removal of toxic metals from aqueous samples. An attempt to regenerate sorbent was made since the saturated sorbents that contain the metal ions are not safe for disposal as they can pollute the environment. Nutrients were analyzed by HPLC, while metals were analyzed using a Varian 220FS Atomic Absorption Spectrometer operated with air/acetylene. Nonedible agricultural materials were found to contain appreciable amounts of plant nutrients such as nitrates (NO₃^-), nitrites (NO₂^-), and phosphates (PO₄^3-) as well as metal ions such as magnesium, copper, and zinc, which are beneficial for plant growth. Results obtained from analysis of sewage water effluent showed that heavy metal and nutrient concentrations decreased in the treatment stage. The utilization of Moringa oleifera seed pods for metal removal from wastewater is viable and would reduce costs for waste disposal and can offer alternatives to conventional methods for the removal of unwanted or toxic species from the environment. It showed potential for removing selected metal ions such as Pb, Cd, Cu, Fe, and Zn from polluted water. This organically treated wastewater is environmentally friendly and may be used for applications which do not require potable water, such as irrigating golf courses, lawns, and crops, or for industrial purposes, if proper measures are taken to ensure its quality.

Bioengineered magnetic graphene oxide microcomposites for bioremediation of chromium in ex situ - A novel strategy for aggrandized recovery by electromagnetic gadgetry

Novel magnetic microcomposites consisting of graphene oxide and iron oxide was synthesized to immobilize metabolically versatile Paracoccus sp. MKU1 and Leucobacter sp. AA7 and tested for the simultaneous adsorption and enhanced biological detoxification of hexavalent chromium (Cr(VI)) from tannery wastewater. This study reports highest chromium adsorption of 272.6 mg/g and 179.3 mg/g with complete reduction of Cr(VI) to Cr(III) by the microcomposites of AA7 and MKU1 from wastewater in a bioreactor (10 L) at large-scale for first time in ex situ. Furthermore, both the microcomposites displayed an enhanced detoxification of tannery wastewater by reducing various physicochemical conditions such as ammonia, nitrate, TDS, fluoride, CaCO_3, Ca, Mg, NO₃ and SO₂ under the permissible limits. Use of electromagnetic device for magnetic microcomposites recovery from bioreactor yielded a maximum of 88% and 80.6% recovery for AA7 and MKU1, respectively. The rate of chromium recuperation achieved following desorption from the microcomposites of AA7 and MKU1 was 90.71% and 93.97%, respectively. Thus, the multifarious benefits including adsorption, metabolic detoxification, recovery, and recuperation by single functional microcomposites seems to be an intriguing and profitable approach for practicing in real-time operations to effectively remove heavy metals from the contaminated wastewater for environmental protection.

Effect of fermentation of chosen vegetables on the nutrient, mineral, and biocomponent profile in human and animal nutrition

In the present study, the dry matter, crude ash, crude protein, ether extract, and energy, macro- (Na, K, Ca, Mg, P), micro- (Zn, Cu, Fe) minerals, heavy metals (Pb, Cd), vitamin C, A, carotene, and phenolic content were determined in chosen raw and fermented vegetables. The dietary intake of several macro- and microconstituents per one serving (100 g or humans and animals: ducks and pigs) was calculated. The fermentation process was found to reduce water and increase fat content in the vegetables. Lower levels of vitamin C and phenols were also found in the fermented vegetables. The vitamin A and carotene content in the fermented carrots and peppers were increased in comparison with the raw vegetables. The fermentation process decreased the concentration of some basic nutrients, mineral content, vitamins C and A, and phenols. Broccoli, peppers, and red beet had the highest levels of the analyzed nutrients and bioconstituents. The fermentation process is regarded by nutritionists as beneficial to human health. The addition of fermented plants is recommended in animal nutrition as well. This process modifies the chemical composition of preserved vegetables, e.g. it reduces the concentration of dietary fiber, and brings favorable effects in poultry and pig nutrition.

Thermochemical study of Cr(VI) sequestration onto chemically modified Areca catechu and its recovery by desorptive precipitation method

A new biosorbent for Cr(VI) sequestration was investigated from betel nut waste (BNW), Areca catechu, by H₂SO₄ charring. Aqueous insolubility and Cr(VI) uptake capacity of native BNW were potentially improved after H₂SO₄ modification due to cross-linking reaction of betel nut cellulose, thereby creating suitable complexation sites for Cr(VI) ion removal. Langmuir isotherm and pseudo second order (PSO) kinetic models described well with the experimental data. A trace amount of Cr(VI) was effectively removed below the safe drinking water standard (WHO, 0.05 mg/L) using charred BNW (CBNW). The negative value of ΔG° evaluated for all the temperatures suggested the spontaneous nature of Cr(VI) sequestration and positive value of ΔH° (42.43±0.13 kJ/mol) confirmed an endothermic reaction. Co-existing NO3−, Cl⁻, Na⁺ and Zn²⁺ ions showed negligible interferences, whereas SO42− and PO43− notably reduced Cr(VI) uptake capacity of CBNW. More than 98% of adsorbed Cr(VI) was desorbed using 1M NaOH solution. A light yellow precipitate of BaCrO₄ was recovered from the desorbed solution after precipitation with BaCl₂ solution. Therefore, the CBNW biosorbent investigated in this work is expected to be a promising material for Cr(VI) sequestration and its recovery from polluted water.

Removal of Pb2+ from Water Using Sustainable Brown Seaweed Phlorotannins

Bioadsorption is a promising technology to sequester heavy metal ions from water, and brown seaweed has been identified as one of the most appropriate adsorbents as it is abundant, low cost, and efficient at removing various metal ion contaminations. The ability to remove heavy metals from water arises from the high concentration of polysaccharides and phlorotannins in brown seaweed; however, remediation can be hampered by the salinity, location, and coexistence of pollutants in the contaminated water. Maintaining the adsorbent properties of brown seaweed while avoiding the fragility of living organisms could allow for the development of better adsorbents. Herein, we demonstrate that polymerized phlorotannin particles, synthesized from phlorotannins extracted from a species of brown seaweed (Carpophyllum flexuosum), were able to remove 460 mg of Pb²⁺ from water per gram of adsorbent. Scanning electron microscopy (SEM), attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), and thermogravimetric analysis (TGA) were used to characterize the polymerization process and the polymerized phlorotannin particles. Importantly, there was no direct correlation between the Pb²⁺ removal capacity and the phlorotannin content of various algal derivatives of three species of brown seaweed, C. flexuosum, Carpophyllum plumosum, and Ecklonia radiata, as all three had similar adsorption capacities despite differences in phlorotannin content. This work shows that naturally abundant, "green" materials can be used to help remediate the environment.