Potassium permanganate-modified eggshell biosorbent for the removal of diclofenac from liquid environment: adsorption performance, isotherm, kinetic, and thermodynamic analyses

This study assess how well diclofenac (DCF) can be separated from aqueous solution using potassium permanganate-modified eggshell biosorbent (MEB). The MEB produced was characterised using XRD, FTIR, and SEM. Batch experiments were conducted to examine and assess the impact of contact time, adsorbent dosage, initial concentration, and temperature on the adsorption capacity of the MEB in the DCF sequestration. The best parameters to obtained 95.64% DCF removal from liquid environment were 0.05 g MEB weight, 50 mg/L initial concentration, and 60 min contact time at room temperature. The maximum DCF sequestration capacity was found to be 159.57 mg/g with 0.05 g of MEB at 298 K. The adsorption isotherm data were more accurately predicted by the Freundlich model, indicating a process of heterogeneous multilayer adsorption. The results of the kinetic study indicated that the pseudo-second-order kinetic models best matched the experimental data. The findings revealed that the dynamic of DCF entrapment is largely chemisorption and diffusion controlled. Based on the values of thermodynamic parameters, the process is both spontaneous and endothermic. The primary processes of DCF sorption mechanism onto the MEB were chemical surface complexation, hydrogen bonding, π-π stacking, and electrostatic interactions. The produced MEB showed effective DCF separation from the aqueous solution and continued to have maximal adsorption capability even after five regeneration cycles. These findings suggest that MEB could be highly efficient adsorbent for the removal of DCF from pharmaceutical wastewater.

Utilizing Chamaerops humilis in removing methylene blue dye from water: an effective approach

Removing dyes, particularly methylene blue, from wastewater is crucial due to their detrimental effects on environmental and human health. Adsorption, recognized as a simple and efficient technique, is frequently employed to eliminate various dyes from water. Although activated carbon is a favored adsorbent for wastewater treatment, its high cost often restricts its use. As a result, there is increasing interest in utilizing inexpensive, natural materials, and waste products as alternative adsorbents. Sawdust from the European fan palm tree, specifically Chamaerops humilis, a widely available and cost-effective by-product, has demonstrated effective dye removal from wastewater. This study explored the impact of various factors such as time, agitation, adsorbent quantity, dye concentration, pH, and temperature on the adsorption of methylene blue using Chamaerops humilis sawdust. Optimal dye adsorption conditions were identified at a temperature of 25 °C, a pH of 8, an adsorbent dosage of 100 mg, a contact time of 120 min, and a dye concentration of 20 mg L-1, achieving a removal efficiency of 93.5%. Moreover, the Langmuir isotherm model described the adsorption dynamics more accurately, suggesting a maximum sorption capacity of 22.7 mg g-1 for the sawdust. Additionally, adsorption kinetics aligned better with the pseudo-second-order model than the pseudo-first-order model, underscoring the efficacy of this method in treating dye-polluted water.

Exploring Ficus religiosa inflorescence powder as an eco-friendly and sustainable solution for the removal of crystal violet with a disposal solution

This study investigates the potential of using Ficus religiosa inflorescence (peepal tree) as an efficient solution for removing crystal violet from simulated and industrial wastewater. Various analyses were conducted to understand the adsorbent's structure, including particle morphology, BET surface area, FTIR, and pHZPC. The adsorption process was studied under different physicochemical factors such as temperature, concentration, contact time, and pH. Results revealed rapid adsorption, with 94.15% removal efficiency within the first 15 min at neutral pH. The highest observed adsorption capacity was 198.03 mg g-1, following pseudo-second-order kinetics (R2 = 0.99), indicating chemisorption. The Langmuir model accurately described the adsorption pathway (R2 = 0.99), showing monolayer adsorption. Thermodynamic analysis indicated an exothermic, feasible, and spontaneous process with increased entropy. The adsorbent could be easily regenerated using a 1:1 MeOH/H2O mixture for up to three cycles, yielding up to 73.86%. Real-time application with industrial effluent containing crystal violet showed up to 44.70% adsorption. The experiments demonstrated reliability with evaluated standard deviations (0.017935-0.000577) and relative standard deviations (0.439-0.673%), confirming statistical reliability. In conclusion, it presents a sustainable and eco-friendly approach for removing crystal violet dye from diverse wastewater sources.

Valorization of Grain and Oil By-Products with Special Focus on Hemicellulose Modification

Hemicellulose is one of the most important natural polysaccharides in nature. Hemicellulose from different sources varies in chemical composition and structure, which in turn affects the modification effects and industrial applications. Grain and oil by-products (GOBPs) are important raw materials for hemicellulose. This article reviews the modification methods of hemicellulose in GOBPs. The effects of chemical and physical modification methods on the properties of GOBP hemicellulose biomaterials are evaluated. The potential applications of modified GOBP hemicellulose are discussed, including its use in film production, hydrogel formation, three-dimensional (3D) printing materials, and adsorbents for environmental remediation. The limitations and future recommendations are also proposed to provide theoretical foundations and technical support for the efficient utilization of these by-products.

A Review Delving into the Factors Influencing Mycelium-Based Green Composites (MBCs) Production and Their Properties for Long-Term Sustainability Targets

Mycelium-based green composites (MBCs) represent an eco-friendly material innovation with vast potential across diverse applications. This paper provides a thorough review of the factors influencing the production and properties of MBCs, with a particular focus on interdisciplinary collaboration and long-term sustainability goals. It delves into critical aspects such as fungal species selection, substrate type selection, substrate preparation, optimal conditions, dehydrating methods, post-processing techniques, mold design, sterilization processes, cost comparison, key recommendations, and other necessary factors. Regarding fungal species selection, the paper highlights the significance of considering factors like mycelium species, decay type, hyphal network systems, growth rate, and bonding properties in ensuring the safety and suitability of MBCs fabrication. Substrate type selection is discussed, emphasizing the importance of chemical characteristics such as cellulose, hemicellulose, lignin content, pH, organic carbon, total nitrogen, and the C: N ratio in determining mycelium growth and MBC properties. Substrate preparation methods, optimal growth conditions, and post-processing techniques are thoroughly examined, along with their impacts on MBCs quality and performance. Moreover, the paper discusses the importance of designing molds and implementing effective sterilization processes to ensure clean environments for mycelium growth. It also evaluates the costs associated with MBCs production compared to traditional materials, highlighting potential cost savings and economic advantages. Additionally, the paper provides key recommendations and precautions for improving MBC properties, including addressing fungal strain degeneration, encouraging research collaboration, establishing biosecurity protocols, ensuring regulatory compliance, optimizing storage conditions, implementing waste management practices, conducting life cycle assessments, and suggesting parameters for desirable MBC properties. Overall, this review offers valuable insights into the complex interplay of factors influencing MBCs production and provides guidance for optimizing processes to achieve sustainable, high-quality composites for diverse applications.

Novel granular bentonite-carbon sorbents: textural characterization, adsorption-desorption isotherm, kinetics, and cost estimation

This research focuses on the synthesis of novel low-cost granular sorbents based on bentonite clay of the Navbahor deposit, dust fraction of Angren brown coal, and agricultural wastes such as straw and sawdust to meet the internal needs of the Republic of Uzbekistan. The impact of the initial mixture ingredients on the structural and textural properties of bentonite-coal sorbents (BCSs) has been studied using X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, optical microscopy, and nitrogen adsorption-desorption analysis. For determining the sorption capacity of BCSs, a standard model substance methylene blue (MB), was applied. It was revealed that the maximum adsorption amount of MB was 5.3 mg∙g-1 during 2 h of contact. Prolonging the contact time to 24 h allowed for more extensive diffusion of dye molecules into the sorbent's pores, increasing the adsorption capacity to 13 mg∙g-1. It was demonstrated that BCSs could be regenerated by strong oxidizing agents such as sulfuric acid and hydrogen peroxide, with sulfuric acid proving more effective. Regeneration fully restores sorption properties, particularly at low dye concentrations (up to 0.2 mg∙ml-1). Despite slight reductions in adsorption capacity over multiple regeneration cycles, the sorbents maintain their structural integrity and durability. It is shown that compared to imported expensive activated carbon, the gross profitability of the in-house production of such granular BCSs within the territory of Uzbekistan increases from 48 to 78%, while the net income increases almost three times.

Synthesis of a Magnetic Nanostructured Composite Sorbent Only from Waste Materials

Water pollution is a big problem for the environment, and thus depollution, especially by adsorption processes, has garnered a lot of interest in research over the last decades. Since sorbents would be used in large quantities, ideally, they should be cheaply prepared in scalable reactions from waste materials or renewable sources and be reusable. Herein, we describe a novel preparation of a range of magnetic sorbents only from waste materials (sawdust and iron mud) and their performance in the adsorption of several dyes (methylene blue, crystal violet, fast green FCF, and congo red). The preparation is performed in a hydrothermal process and is thus easily scalable and requires little sophisticated equipment. The magnetic nanostructured materials were analyzed using FTIR, VSM, SEM/EDX, XRD, and XPS. For crystal violet as a pollutant, more in-depth adsorption studies were performed. It was found that the best-performing magnetic sorbent had a maximum sorption capacity of 97.9 mg/g for crystal violet (methylene blue: 149.8 mg/g, fast green FCF: 52.2 mg/g, congo red: 10.5 mg/g), could be reused several times without drastic changes in sorption behavior, and was easily separable from the solution by simply applying a magnet. It is thus envisioned to be used for depollution in industrial/environmental applications, especially for cationic dyes.

Some Unmodified Household Adsorbents for the Adsorption of Benzalkonium Chloride-A Kinetic and Thermodynamic Case Study for Commercially Available Paper

The extensive use of biocide surfactant benzalkonium chloride (BAC) during the SARS-CoV-2 pandemic has led to the buildup of this hazardous chemical in waste, surface and groundwater. e The study aims to elucidate whether various low-cost household materials are suitable, in their unmodified and untreated form, to effectively adsorb BAC from its aqueous solutions.. Additionally, if a proper adsorbent is identified, a description of the kinetics and thermodynamics of the process is also targeted. From among the five tested materials, a commercially available white household paper towel was chosen to best satisfy the criteria of low price, large availability, and standardization degree, as well as high adsorption capacity within a fairly short time window needed until equilibrium. Batch experiments were carried out with a commercial mixture of BAC-12 and BAC-14 within a temperature range of 18-45 degrees Celsius, and a 25-100 mg/g BAC/adsorbent initial mass ratio range, respectively. The overall process follows a pseudo-second-order kinetic law, with an apparent activation energy of 73.35 KJ/mole. Both the Langmuir and the Redlich-Peterson isotherms describe the equilibrium data at 298 K well, with a Gibbs free energy of -20.64 KJ/mole. These findings are in agreement with previous reports and suggest a hybrid but chemisorption-dominated process.

Adsorption of Safranin O Dye by Alginate/Pomegranate Peels Beads: Kinetic, Isotherm and Thermodynamic Studies

Water pollution is regarded as a dangerous problem that needs to be resolved right away. This is largely due to the positive correlation between the increase in global population and waste production, especially food waste. Hydrogel beads based on sodium alginate (Alg) and pomegranate fruit peels (PP) were developed for the adsorption of Safranin O dye (SO) in aqueous solutions. The obtained Alg-PP beads were widely characterized. The effects of the contact time (0-180 min), initial concentration (10-300 mg/L), initial pH (2-10), adsorbent dosage (1-40 g/L) and the temperature (293-333 K) were investigated through batch tests. The data proved that the adsorption kinetics of SO reached equilibrium within 30 min and up to 180 min. The dye adsorption is concentration dependent while a slight effect of pH was observed. The adsorption data of SO onto synthesized beads follow the pseudo second-order model. The experimental data fitted very well to Langmuir model with correlation factor of 0.92 which demonstrated the favourable nature of adsorption. The maximum adsorption capacity of Alg-PP could reach 30.769 mg/g at 293 K. Calculation of Gibbs free energy and enthalpy indicated that adsorption of SO onto Alg-PP is spontaneous (negative ΔG) and endothermic (ΔH = 9.30 kJ/mol). Analysis of diffusion and mass transport phenomena were presented. The removal efficiency was found to be 88% at the first cycle and decreased to 71% at the end of the seventh cycle. The reported results revealed that the Alg-PP beads could be used as a novel natural adsorbent for the removal of high concentrated solutions of Safranin O which is a cationic dye from liquid affluents and as future perspective, it can be used to remove various pollutants from wastewater.

Kinetic studies of the removal of methylene blue from aqueous solution by biochar derived from jackfruit peel

Kinetic studies play an instrumental role in determining the most appropriate reaction rate model for industrial-scale applications. This study focuses on the kinetics of methylene blue (MB) adsorption from aqueous solutions by biochar derived from jackfruit peel. Various kinetic models, including pseudo-first-order (PFO), pseudo-second-order (PSO), intra-diffusion, and Elovich models, were applied to study MB adsorption kinetics of jackfruit peel biochar. The experiments were performed with two initial concentrations of MB (24.23 mg/L and 41.42 mg/L) over a span of 240 min. Our findings emphasized that the Elovich model provided the best fit of the experimental data for MB adsorption. When compared to other materials, biochar from jackfruit peel emerges as an eco-friendly adsorbent for dye decolorization, with potential applications in the treatment of environmental pollution.

A critical review on the biosynthesis, properties, applications and future outlook of green MnO2 nanoparticles

MnO2 nanoparticles have played a vital role in biomedical, catalysis, electrochemical and energy storage fields, but requiring toxic chemicals in the fabrication intercepts their applications. There is an increasing demand for biosynthesis of MnO2 nanoparticles using green sources such as plant species in accordance with the purposes of environmental mitigation and production cost reduction. Here, we review recent advancements on the use of natural compounds such as polyphenols, reducing sugars, quercetins, etc. Extracted directly from low-cost and available plants for biogenic synthesis of MnO2 nanoparticles. Role of these phytochemicals and formation mechanism of bio-medicated MnO2 nanoparticles are shed light on. MnO2 nanoparticles own small particle size, high crystallinity, diverse morphology, high surface area and stability. Thanks to higher biocompatibility, bio-mediated synthesized MnO2 nanoparticles exhibited better antibacterial, antifungal, and anticancer activity than chemically synthesized ones. In terms of wastewater treatment and energy storage, they also served as efficient adsorbents and catalyst. Moreover, several aspects of limitation and future outlook of bio-mediated MnO2 nanoparticles in the fields are analyzed. It is expected that the present work not only expands systematic understandings of synthesis methods, properties and applications MnO2 nanoparticles but also pave the way for the nanotechnology revolution in combination with green chemistry and sustainable development.

Augmented dye eradication from wastewater using alkali-aided, reinforced waste acacia (Acacia auriculiformis) leaves

The present investigation demonstrates the augmented dye scavenging from wastewater using alkali-mutated acacia (Acacia auriculiformis) leaves powder. The material was synthesized by mild chemical activation by using 0.1 M sodium hydroxide as an activator under room temperature stirring for 3h and isolated as a dark brown powder. The material was characterized using FTIR, FESEM, XRD, and pHzpc; and tested successfully with crystal violet and methylene blue. While FTIR confirms the presence of polyphenolic and polysaccharide moieties, FESEM reveals unprecedented circular hollow pipe-like channels decorated in a highly ordered fashion, facing pores for optimum dye uptake. The adsorption is tunable with working pH, and the maximum adsorption capacities are 67.25 and 78.55 mg g-1 for CV and MB. Both adsorption process follows Langmuir isotherm (R2 = 0.994) and pseudo-2nd-order kinetics (R2 = 0.999). Thermodynamic analysis verifies a spontaneous process with an endothermic interaction beside an elevated degree of randomness. About 80% of the spent material could be regenerated using 1:1 methanol/water. Analysis of industrial effluent suggests 37% removal per cycle, with an operating ceiling of 95%. To wind up, due to huge availability, porous nature, and superior adsorption capacity over other phytosorbents, NaOH-activated acacia leaves could be considered as techno-economic and potential scavengers for sustainable water treatment.

One-pot synthesis of metal oxide-clay composite for the evaluation of dye removal studies: Taguchi optimization of parameters and environmental toxicity studies

The present study demonstrates the synthesis of eco-friendly metal oxide-clay composites (MgO-clay and CaO-clay) with phytochemical functionalization. The physical and chemical properties of prepared composites were characterized using standard techniques viz. scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The effect of pH on the dye adsorption capability of the synthesized composites was studied. The adsorption of an anionic dye methyl orange (MO) and a cationic due methylene blue (MB) was favored in the acidic and basic regions, respectively. The Taguchi design approach was adopted for the removal of MO and MB from wastewater using the synthesized composites. The obtained results suggest that initial dye concentration and composite dosage were the most influential parameters in dye removal among all the studied parameters. The adsorption experiments were carried out using MgO-clay and CaO-clay composites with the optimum conditions obtained from Taguchi optimization to validate the predicted response. The experimental parameters viz. the effect of contact time, initial dye concentration, and solution temperature were studied for screened composite (CaO-clay) with optimized conditions. The obtained results were interpreted using standard isotherms and kinetic models. A maximum adsorption capacity of 571 ± 10 and 859 ± 14 mg g^-1 was obtained from the Langmuir adsorption isotherm for MO and MB, respectively. Regeneration studies suggested that the CaO-clay composite can be utilized up to 3 cycles with reduced adsorption capacity of the dyes over cycles due to the solid binding nature of dyes on the CaO-clay composite. The fresh and utilized CaO-clay composite were tested for their environmental toxicity analysis using ecologically important soil microorganisms. The obtained results suggested no detrimental effects on soil microbe's functionality, indicating their threat-free disposal in the soil environment.

Brilliant blue FCF dye adsorption using magnetic activated carbon from Sapelli wood sawdust

Sapelli wood sawdust-derived magnetic activated carbon (SWSMAC) was produced by single-step pyrolysis using KOH and NiCl₂ as activating and magnetization agents. SWSMAC was characterized by several techniques (SEM/EDS, N₂ adsorption/desorption isotherms, FTIR, XRD, VSM, and pH_PZC) and applied in the brilliant blue FCF dye adsorption from an aqueous medium. The obtained SWSMAC was a mesoporous material and showed good textural properties. Metallic nanostructured Ni particles were observed. Also, SWSMAC exhibited ferromagnetic properties. In the adsorption experiments, adequate conditions were an adsorbent dosage of 0.75 g L^-1 and a solution pH of 4. The adsorption was fast, and the pseudo-second-order demonstrated greater suitability to the kinetic data. The Sips model fitted the equilibrium data well, and the maximum adsorption capacity predicted by this model was 105.88 mg g^-1 (at 55 °C). The thermodynamic study revealed that the adsorption was spontaneous, favorable, and endothermic. Besides, the mechanistic elucidation suggested that electrostatic interactions, hydrogen bonding, π-π interactions, and n-π interactions were involved in the brilliant blue FCF dye adsorption onto SWSMAC. In summary, an advanced adsorbent material was developed from waste by single-step pyrolysis, and this material effectively adsorbs brilliant blue FCF dye.

A comprehensive review on the metal-based green valorized nanocomposite for the remediation of emerging colored organic waste

In today's era, "green" synthesis is an emerging research trend. It has gained widespread attention owing to its dynamic behavior, reliability, simplicity, sustainability, and environment friendly approach for fabricating various nanomaterials. Green fabrication of metal/metal oxides nanomaterials, hybrid materials, and other metal-based nanocomposite can be utilized to remove toxic colored aqueous pollutants. Nanomaterials synthesized by using green approach is considered to be the significant tool to minimize unwanted or harmful by-products otherwise released from traditional synthesis methods. Various kinds of biosynthesized nanomaterials, such as animal waste and plant-based, have been successfully applied and well documented in the literature. However, their application part, especially for the cure of colored organic polluted water, has not been reported as a single review article. Therefore, the current work aims to assemble reports on using novel biosynthesized green metal-based nanomaterials to exclude harmful dyes from polluted water.

Comparative study for removal of cationic and anionic dyes using alginate-based hydrogels filled with citric acid-sawdust/UiO-66-NH2 hybrid

Nowadays, a big challenge is developing a sustainable and effective method for removing contaminants like dyes from aqueous solutions. In this regard, Zr-based metal-organic framework (UiO-66-NH₂) and sawdust as the ideal adsorbents were used. Due to their low separation in adsorption processes, embedding into alginate and obtaining composite beads are suggested as a suitable strategy. The achieved Ca-alginate/citric acid (CA)-sawdust/UiO-66-NH₂ hydrogel beads were used to compare cationic and anionic dyes removal. This sorbent indicated an excellent selectivity for removing methylene blue versus methyl orange in a binary system. pH = 6, adsorbent amount = 80 mg, methylene blue concentration = 10 mg/L, and contact time = 420 min were achieved as optimal parameters on methylene blue adsorption with an adsorption capacity of about 26 mg/g. The removal process of methylene blue followed linear Freundlich isotherm and nonlinear pseudo-2nd-order kinetic models. The regeneration test demonstrated methylene blue removal efficiency higher than about 89 % after 9 cycles. According to the outcomes, methylene blue could be attached to the adsorbent surface through the electrostatic, hydrogen bonding, and π-π interactions of the aromatic rings. These results confirm the potential of Ca-alginate/CA-sawdust/UiO-66-NH₂ hydrogel beads as a selective bio-sorbent for cationic dye removal.

Adsorptive Features of Magnetic Activated Carbons Prepared by a One-Step Process towards Brilliant Blue Dye

Water pollution by dyes has been a major environmental problem to be tackled, and magnetic adsorbents appear as promising alternatives to solve it. Herein, magnetic activated carbons were prepared by the single-step method from Sapelli wood sawdust, properly characterized, and applied as adsorbents for brilliant blue dye removal. In particular, two magnetic activated carbons, MAC1105 and MAC111, were prepared using the proportion of biomass KOH of 1:1 and varying the proportion of NiCl₂ of 0.5 and 1. The characterization results demonstrated that the different proportions of NiCl₂ mainly influenced the textural characteristics of the adsorbents. An increase in the surface area from 260.0 to 331.5 m² g^-1 and in the total pore volume from 0.075 to 0.095 cm³ g^-1 was observed with the weight ratio of NiCl₂. Both adsorbents exhibit ferromagnetic properties and the presence of nanostructured Ni particles. The different properties of the materials influenced the adsorption kinetics and equilibrium of brilliant blue dye. MAC111 showed faster kinetics, reaching the equilibrium in around 10 min, while for MAC1105, it took 60 min for the equilibrium to be reached. In addition, based on the Sips isotherm, the maximum adsorption capacity was 98.12 mg g^-1 for MAC111, while for MAC1105, it was 60.73 mg g^-1. Furthermore, MAC111 presented the potential to be reused in more adsorption cycles than MAC1105, and the use of the adsorbents in the treatment of a simulated effluent exhibited high effectiveness, with removal efficiencies of up to 90%.

Adsorption of Arsenic, Lead, Cadmium, and Chromium Ions from Aqueous Solution Using a Protonated Chabazite: Preparation, Characterization, and Removal Mechanism

The adsorption of As(V), Pb(II), Cd(II), and Cr(III) ions from aqueous solutions on natural and modified chabazite was studied. The functionalization of chabazite was performed via a protonation and calcination with the aim of generating Lewis acid sites to improve its anion exchange properties. The surface and physicochemical properties of both adsorbents were studied and compared. The adsorption isotherms of tested heavy metal ions were quantified and modeled to identify the best isotherm equation. Steric parameters for the adsorption of these ions were also calculated with a monolayer statistical physics model. Natural chabazite showed the maximum adsorption capacity for Pb(II), while the modified zeolite improved its As(V) properties in 79%. These results showed that the modified zeolite was able to remove both cations and anions from aqueous solution. The application of this functionalized chabazite can be extended for the removal of other anionic pollutants from water, thus opening the possibility of preparing new adsorbents with tailored properties for water treatment.

Highly ordered CaO from cuttlefish bone calcination for the efficient adsorption of methylene blue from water

The aim of this study is to synthesize cheap and highly ordered CaO from cuttlefish bone (CFB) as a green alternative to conventional adsorbents such as activated carbon. This study focuses on the synthesis of highly ordered CaO via calcination of CFB, at two different temperatures (900 and 1000°C) and two holding times (0.5 and 1 h), as a potential green route for water remediation. The as-prepared highly ordered CaO was tested as an adsorbent using methylene blue (MB) as a model compound for dye contaminants in water. Different CaO adsorbent doses (0.05, 0.2, 0.4, and 0.6 g) were used, keeping the MB concentration fixed at 10 mg/L. The morphology and crystalline structure of the CFB before and after calcination was characterized via scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses, while the thermal behavior and surface functionalities were characterized by thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy, respectively. Adsorption experiments using different doses of CaO synthesized at 900°C for 0.5 h showed an MB removal efficiency as high as 98% by weight using 0.4 g (adsorbent)/L(solution). Two different adsorption models, the Langmuir adsorption model and the Freundlich adsorption model, along with pseudo-first-order and pseudo-second-order kinetic models, were studied to correlate the adsorption data. The removal of MB via highly ordered CaO adsorption was better modeled by the Langmuir adsorption isotherm giving (R² =0.93), thus proving a monolayer adsorption mechanism following pseudo-second-order kinetics (R²= 0.98), confirming that chemisorption reaction occurs between the MB dye molecule and CaO.

Biomass conversion of agricultural waste residues for different applications: a comprehensive review

Agricultural waste residues (agro-waste) are the source of carbohydrates that generally go in vain or remain unused despite their interesting morphological, chemical, and mechanical properties. With rapid urbanization, there is a need to valorize this waste due to limited non-renewable resources. Utilizing agro-waste also prevents the problems like burning and inefficient disposal that otherwise lead to immense pollution worldwide. In addition, conversion of biomass to value-added products like earthen cups, weaving baskets, and bricks is equally beneficial for the rural population as it provides secondary income, creates jobs, and improves rural people's lifestyles. This review paper will discuss an overview of different applications utilizing agro-waste residues. In particular, agro-wastes used as construction material, bio-fertilizers, pulp and paper products, packaging products, tableware, heating applications, biocomposites, nano-cellulosic materials, soil stabilizers, bioplastics, fire-retardant additive, dye removal, and biofuels will be summarized. Finally, several commercially available agro-waste products will also be discussed, emphasizing the circular economy.

Exploring the promising potential of fallen bamboo leaves (Bambusa bambos) for efficient removal of crystal violet from wastewater

Fallen bamboo leaves (Bambusa bambos), hereinafter BL have been designed to be transformed into an efficient and sustainable adsorbent for the removal of crystal violet (CV) dye from wastewater with up to 95% scavenging ability. BL have been characterized by Fourier transform infrared (FTIR) spectra, field emission scanning electron microscopy (FESEM), and zero point charge (pHzpc). The maximum adsorption capacity is 30 mg/g at pH 10. Physico-chemical parameters have been investigated concerning pH, contact time, initial concentration, and coexistent ions. Pseudo-second-order kinetics is followed best (R² =0.999) signifying a chemisorption pathway. Besides, intra-particle diffusion plays a governing role in the film diffusion of crystal violet into the core of the adsorbent. Langmuir isotherm model fits best (R²=0.972) suggesting a uniform, monolayer, and homogeneous adsorption. Regeneration was successful with methanol (65%) and reusability was tested for three cycles and was found to retain activity up to 80%. Analysis of CV containing industrial effluent suggests that a 36.8% reduction is possible with BL. The effect of co-existent ions suggests little influence on the adsorption. Compared to other contemporary and relevant adsorbents, it can be concluded that BL can be exercised for the sustainable decontamination of CV-containing wastewater.

Potential applications of spent adsorbents and catalysts: Re-valorization of waste

Water pollution has increased with the growth of human population and its industrial activities. Textile effluents constitute a particular threat due to the presence of heavy metals and dyes. Adsorption is one of the most applied technologies in contaminant removal owing to its high efficiency, low cost, practical implementation and possibility to operate in several experimental conditions. However, this process implies the generation of spent materials, representing a limitation to scale-up. Although the applications of exhausted solids in effluent treatments have not been extensively reviewed before, their reutilization appears to be an environmentally and economically attainable alternative. This work summarizes the potential value of solids post-use. The open literature reports that spent adsorbents based on polysaccharides with iron oxides may adsorb up to 1 g g^-1 of organic pollutants and up to near 100% of metallic ions from wastewater (Cu²⁺, Cd²⁺, Zn²⁺, Pb²⁺). The studied conditions vary from 30 to 60 °C, 0,05 to 6 g L^-1 of adsorbent, 10 mg L^-1 to 250 mg L^-1 of organic pollutants (dyes) and pH between 2 and 8. Spent adsorbents in dye removal have proven to have near 95% efficiency in metallic ion adsorption. Otherwise, the spent solids could be applied to remove Ca²⁺ and Mg²⁺ to decrease the hardness of water. Furthermore, at the end-of-life, these materials could be used in cement and ceramic production. To achieve these aims, it is necessary to design the bioadsorbents and biocatalysts considering not only their primary uses (as adsorbent of organic pollutants), but also secondary applications (as toxic metal or hardness removal) and even their final destination (as additive in ceramic or cement production). Finally, further studies are required on the composition, properties, stability at long-term and the life-cycle cost of these materials when they are applied in the construction industry.

Adsorptive Removal of Methylene Blue Dye Using Biowaste Materials: Barley Bran and Enset Midrib Leaf

In this study, several biowaste materials are screened for adsorptive removal of methylene blue (MB) from synthetic water. Among the tested adsorbents, barley (Hordeum vulgare) bran (BB) and enset (Ensete ventricosum midrib leaf, EVML) were selected for further evaluation of MB (a model cationic dye) adsorption. Batch MB adsorption performance of BB and EVML adsorbents was significantly high in a wide pH range (4-9). The well fitting of experimental data with pseudosecond-order kinetic model suggests a monolayer adsorption of MB. The MB adsorption onto both adsorbents was fit well with the Langmuir isotherm model with maximum MB adsorption capacities of 63.2 mg/g (BB) and 35.5 mg/g (EVML). The biowaste materials exhibit considerable adsorption capacity for cationic dye (MB), perform well under acidic and basic conditions, and are reusable. Therefore, the use of these materials as adsorbents may have an environmental benefit in terms of the conversion of wastes into valuable materials. Further studies are suggested to investigate the performance of these adsorbents in a continuous mode using real wastewater.

Biodegradable cellulose nanocrystals hydrogels for removal of acid red 8 dye from aqueous solutions

Biodegradable cellulose nanocrystals hydrogels (CNCsH) were synthesized from cellulose nanocrystals (CNCs) which were prepared from office wastepaper (OWP) by a chemical crosslinking method using epicholorohydrin (ECH) as a cross-linker. CNCsH were tested for their swelling behavior and biodegradability and the point of zero charge had been determined. The ability of CNCsH for removing the Acid Red 8 (AR8) anionic dye from its aqueous solution was evaluated. The different parameters affecting removal of the dye, such as pH, initial concentration of dye, content of CNCs, temperature and adsorbent dosage were investigated. The optimum conditions for 68% removal efficiency were pH = 1, initial concentration of dye = 10 ppm, contact time = 105 min, CNCs content = 5% and CNCsH dosage = 0.5 g at 30 °C. The adsorption isotherms, kinetics, and thermodynamic parameters have been studied. The results showed an appropriate fit for Langmuir adsorption isotherm and pseudo-second order kinetics model with an adsorption capacity of 17.12 mg/g. According to the obtained values of thermodynamic parameters, the removal of Acid red 8 by CNCs hydrogels was exothermic spontaneous process.

Equilibrium, Kinetic, and Thermodynamic Studies of Cationic Dyes Adsorption on Corn Stalks Modified by Citric Acid

The modification of agricultural wastes and their use as low-cost and efficient adsorbents is a prospective pathway that helps diminish waste and decrease environmental problems. In the present research, the natural adsorption capacity of corn stalks (CS) was improved by modification of their surface with citric acid. The adsorption capacity of the modified corn stalks (CS-C) was determined with the help of cationic dyes (methylene blue and malachite green). The equilibrium, kinetics, and thermodynamics of the cationic dyes on CS-C were studied. The Langmuir isotherm model best fitted the data both for methylene blue and malachite green adsorption on CS-C. The adsorption kinetics of the cationic dyes was well described by the pseudo-second order model. Thermodynamic studies revealed that adsorption of the cationic dyes on CS-C was an endothermic process. Negative results of ΔGo (between −31.8 and −26.3 kJ mol−1) indicated that the adsorption process was spontaneous in all the tested temperatures. The present study verified that citric acid-modified corn stalks can be used as a low-cost and effective adsorbent for removal of cationic dyes from aqueous solutions.

Binary adsorption of [Pb(II) + Co(II)] from aqueous solution using thiolated saw dust

Technology advancement has contributed to an increase in industrial activities, resulting in the introduction of metal ions into water resources at concentrations well above the WHO limits. Heavy metals are highly toxic and carcinogenic; they usually occur as multicomponent mixtures in the aquatic environment. In the present study, batch experiments have been conducted to study the dependence of varying concentration, time, pH and temperature on the uptake of Pb(II) as a pure component under equilibrium conditions using thiolated saw dust. Saw dust has been chemically modified with thioglycolic acid and characterised using proximate and FTIR analyses, the degree of thiolation has also been determined. To determine the effect of the presence of Co(II) ions on the uptake of Pb(II) ions, batch experiments for [Pb(II) + Co(II)] mixture have been carried out for concentration ratios of 1:0, 1:1, 1:2, 1:3, 1:4 of Pb:Co at pH 5 and data has been interpreted using Langmuir competitive isotherm, which shows that adsorption of Pb(II) has been suppressed by the presence of Co(II) ions in the binary solution, hence the adsorption process is antagonistic in nature. The study also indicates the possibility of simultaneous removal of both metal ions using low cost bioadsorbent, which is economical especially for application in small-scale industries.

Factors Affecting Synthetic Dye Adsorption; Desorption Studies: A Review of Results from the Last Five Years (2017-2021)

The primary, most obvious parameter indicating water quality is the color of the water. Not only can it be aesthetically disturbing, but it can also be an indicator of contamination. Clean, high-quality water is a valuable, essential asset. Of the available technologies for removing dyes, adsorption is the most used method due to its ease of use, cost-effectiveness, and high efficiency. The adsorption process is influenced by several parameters, which are the basis of all laboratories researching the optimum conditions. The main objective of this review is to provide up-to-date information on the most studied influencing factors. The effects of initial dye concentration, pH, adsorbent dosage, particle size and temperature are illustrated through examples from the last five years (2017-2021) of research. Moreover, general trends are drawn based on these findings. The removal time ranged from 5 min to 36 h (E = 100% was achieved within 5-60 min). In addition, nearly 80% efficiency can be achieved with just 0.05 g of adsorbent. It is important to reduce adsorbent particle size (with Φ decrease E = 8-99%). Among the dyes analyzed in this paper, Methylene Blue, Congo Red, Malachite Green, Crystal Violet were the most frequently studied. Our conclusions are based on previously published literature.

Sawdust, a versatile, inexpensive, readily available bio-waste: From mother earth to valuable materials for sustainable remediation technologies

Sawdust or wood shaving is a relatively abundant and inexpensive lignocellulosic compound, which is provided by mother nature. It is a waste of industry and agriculture, that is found in large quantities and has disposal problems. Nowadays, waste management (like sawdust) and research on converting it to different compounds for special applications and goals have been receiving tremendous attention. So, introducing sawdust as a kind of interesting bio-waste and turn it into wealth for diverse utilizations can be mentioned as the main goal of this overview. In this regard, in the first part, sawdust structure and properties are considered. It is then followed by highlighting its wide applications in sustainable water remediation technology, production of activated carbon, oil-water separation, and high-performance composites fabrication. Please come on to start a journey on this motivating topic.

Investigation of Seeds and Peels of Citrullus colocynthis as Efficient Natural Adsorbent for Methylene Blue Dye

Natural adsorbents as low-cost materials have been proved efficient for water remediation and have significant capacity for the removal of certain chemicals from wastewater. The present investigation aimed to use Citrullus colocynthis seeds (CCSs) and peels (CCPs) as an efficient natural adsorbent for methylene blue (MB) dye in an aqueous solution. The examined biosorbents were characterized using surface area analyzer (BET), scanning electron microscope (SEM), thermogravimetric analyzer (TGA) and Fourier transform infra-red (FT-IR) spectroscopy. Batch adsorption experiments were conducted to optimize the main factors influencing the biosorption process. The equilibrium data for the adsorption of MB by CCSs were best described by the Langmuir isotherm followed by the Freundlich adsorption isotherms, while the equilibrium data for MB adsorption by CCPs were well fitted by the Langmuir isotherm followed by the Temkin isotherm. Under optimum conditions, the maximum biosorption capacity and removal efficiency were 18.832 mg g−1 and 98.00% for MB-CCSs and 4.480 mg g−1 and 91.43% for MB-CCPs. Kinetic studies revealed that MB adsorption onto CCSs obeys pseudo-first order kinetic model (K1 = 0.0274 min−1), while MB adsorption onto CCPs follows the pseudo-second order kinetic model (K2 = 0.0177 g mg−1 min−1). Thermodynamic studies revealed that the MB biosorption by CCSs was endothermic and a spontaneous process in nature associated with a rise in randomness, but the MB adsorption by CCPs was exothermic and a spontaneous process only at room temperature with a decline in disorder. Based on the obtained results, CCSs and CCPSs can be utilized as efficient, natural biosorbents, and CCSs is promising since it showed the highest removal percentage and adsorption capacity of MB dye.

Sawdust for the Removal of Heavy Metals from Water: A Review

The threat of the accumulation of heavy metals in wastewater is increasing, due to their abilities to inflict damage to human health, especially in the past decade. The world’s environmental agencies are trying to issue several regulations that allow the management and control of random disposals of heavy metals. Scientific studies have heavily focused on finding suitable materials and techniques for the purification of wastewaters, but most solutions have been rejected due to cost-related issues. Several potential materials for this objective have been found and have been compared to determine the most suitable material for the purification process. Sawdust, among all the materials investigated, shows high potential and very promising results. Sawdust has been shown to have a good structure suitable for water purification processes. Parameters affecting the adsorption mechanism of heavy metals into sawdust have been studied and it has been shown that pH, contact time and several other parameters could play a major role in improving the adsorption process. The adsorption was found to follow the Langmuir or Freundlich isotherm and a pseudo second-order kinetic model, meaning that the type of adsorption was a chemisorption. Sawdust has major advantages to be considered and is one of the most promising materials to solve the wastewater problem.

Adsorptive decontamination of paper mill effluent by nano fly ash: response surface methodology, adsorption isotherm and reusability studies

In the present study, adsorption of colour and other pollutants from agro-based paper mill effluent onto fabricated coal fly ash nanoparticles (CFA-N) have been investigated. Response surface methodology was applied to evaluate the operational conditions for maximum ouster of colour from effluent by nano structured CFA-N. Maximum reduction in colour (92.45%) and other pollutants were obtained at optimum conditions: 60 min interaction time, 60 g/L adsorbent dosage and 80 rpm agitation rate. The regression coefficient values (adjusted R² = 0.7169; predicted R² = 0.7539) established harmony between predicted and the experimental data. The adsorption equilibrium results matched perfectly with both Langmuir and Freundlich isotherms with maximum adsorption capacity of 250 platinum-cobalt/g. Additionally, the efficacy of CFA-N was also assessed in a continuous column mode. Furthermore, the feasibility of treated effluent for irrigation purpose was checked by growing the plant Solanum lycopersicum. Overall, the findings demonstrated the outstanding role of inexpensive and abundantly available CFA-N in treatment of paper mill effluent to the required compliance levels.