Agricultural biomass-derived magnetic adsorbents: Preparation and application for heavy metals removal

Carbon and metal based magnetic porous materials - Role in drug removal: A Comprehensive review

Development of effective adsorbents for the removal of contaminants from wastewater is indispensable due to increasing water scarcity and a lack of pure drinking water, which are prevailing as a result of rapid industrialization and population growth. Recently, the development of new adsorbents and their effective use without generating secondary waste is receiving huge consideration. In order to protect the environment from primary and secondary pollution, the development of adsorbents from wastes and their recycling have become conventional practices aimed at waste management. As a result, significant progress has been made in the synthesis of new porous carbon and metal-organic frameworks as adsorbents, with the objective of using them for the removal of pollutants. While many different kinds of pollutants are produced in the environment, drug pollutants are the most vicious because of their tendency to undergo significant structural changes, producing metabolites and residues with entirely different properties compared to their parent compounds. Chemical reactions involving oxidation, hydrolysis, and photolysis transform drugs. The resulting compounds can have detrimental effects on living beings that are present in soil and water. This review stresses the development of adsorbents with adjustable porosities for the broad removal of primary drug pollutants and their metabolites, which are formed as a result of drug transformations in environmental matrices. This keeps adsorbents from building up in the environment and prevents them from becoming significant pollutants in the future. Additionally, it stops secondary pollution caused by the deterioration of the used adsorbents. Focus on the development of effective adsorbents with flexible porosities allows for the complete removal of coexisting contaminants and makes a substantial contribution to wastewater management. In order to concentrate more on the development of flexible pore adsorbents, it is crucial to comprehend the milestones reached in the research and applications of porous magnetic adsorbents based on metal and carbon, which are discussed here.

Valorization of lignocellulosic biomass into sustainable materials for adsorption and photocatalytic applications in water and air remediation

An exponential rise in global pollution and industrialization has led to significant economic and environmental problems due to the insufficient application of green technology for the chemical industry and energy production. Nowadays, the scientific and environmental/industrial communities push to apply new sustainable ways and/or materials for energy/environmental applications through the so-called circular (bio)economy. One of today's hottest topics is primarily valorizing available lignocellulosic biomass wastes into valuable materials for energy or environmentally related applications. This review aims to discuss, from both the chemistry and mechanistic points of view, the recent finding reported on the valorization of biomass wastes into valuable carbon materials. The sorption mechanisms using carbon materials prepared from biomass wastes by emphasizing the relationship between the synthesis route or/and surface modification and the retention performance were discussed towards the removal of organic and heavy metal pollutants from water or air (NO_x, CO₂, VOCs, SO₂, and Hg⁰). Photocatalytic nanoparticle-coated biomass-based carbon materials have proved to be successful composites for water remediation. The review discusses and simplifies the most raised interfacial, photonic, and physical mechanisms that might take place on the surface of these composites under light irradiation. Finally, the review examines the economic benefits and circular bioeconomy and the challenges of transferring this technology to more comprehensive applications.

Fir sawdust as a low-cost and easily recyclable adsorbent: efficient removal of Pb(II), Cu(II), and Zn(II) contaminants from wastewater

The main pollution sources of heavy metals are the arbitrary discharge of industrial wastewater and waste residues, which cause serious harm to the water environment, soil environment, and human health. In this study, following the principle of waste utilization, a gel adsorbent (AA-SW-AMPS) was prepared by microwave-assisted chemical cross-linking using fir sawdust as raw material. A scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and swelling dynamic experiments were used to investigate the microstructure, reaction mechanism, and water absorption performance of AA-SW-AMPS. The N₂ adsorption-desorption curve shows that the porous structure of AA-SW-AMPS creates 240.75 cm²/g of specific surface area to enable excellent heavy-metal sorption. It was determined by adsorption experiments that the optimal adsorption state was when the dosage of AA-SW-AMPS was 5 g/L, the pH of the solution was 5, the adsorption time was 45 min, and the initial heavy metal ion concentration was 250 mg/L. In addition, the adsorption mechanism was investigated using adsorption dynamics, adsorption isotherm, and Materials Studio simulation. The results show that the maximum adsorption capacities of AA-SW-AMPS for Pb(II), Cu(II), and Zn(II) were 253.49 mg/g, 237.29 mg/g, and 232.15 mg/g, respectively, and the adsorption mechanism is monolayer chemisorption. The adsorbent showed great potential in removing heavy metals from wastewater.

One-step in-situ sustainable synthesis of magnetic carbon nanocomposite from corn comb (MCCC): agricultural biomass valorisation for pollutant abatement in wastewater

This study explored a novel, eco-friendly, sustainable, low-cost, and abundantly available corn comb (CC) agricultural biomass waste-derived one-step in-situ synthesis of magnetic carbon (MCCC) as an efficient adsorbent for water decontamination applications. Herein, we developed a robust and easily separable MCCC by carbonization of Fe(NO₃)₃.9H₂O single iron salt-soaked CC at 500 °C for 5 h. The as-synthesized MCCC was confirmed for their physicochemical properties by various characterization techniques viz. scanning electron microscopy (SEM), high-resolution transmission emission microscopy (HR-TEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface area measurements by Brunauer-Emmett-Teller (BET) study, Raman analysis, and magnetic behavior by VSM analysis. The adsorption properties of MCCC on prototypical pollutant methylene blue (MB) was monitored depending on the effect of pH, adsorbent dose, contact time, and varying concentrations of MB. Especially, the π-π interactions played important role in the adsorption of MB at acidic pH (pH = 4). The MCCC displayed a maximum uptake capacity of 120.73 ± 0.63 mg/g toward MB. The Langmuir, Freundlich, and Temkin adsorption isotherm models were fitted with determined coefficient (R²) values of 0.99, 0.95, and 0.96 respectively. The kinetics of the adsorption process was well fitted with a pseudo-second-order model (R² = 0.99). Most significantly, the as-designed easily separable, and reusable adsorbent, MCCC was effectively applied for the abatement of pollutants, different kinds of dyes, pesticides, and industrial wastewater samples. The sustainable, affordable, and waste to wealth-based MCCC with a simple synthesis methodology can be fruitfully applicable for environmental remediation and water decontamination.

Adsorption of pollutants in wastewater via biosorbents, nanoparticles and magnetic biosorbents: A review

Adsorption has gained much attention as one of the efficient approaches to remediate the contaminants in wastewater. Herein, this critical review focuses on the preparation, modification, application and regeneration of the biosorbents, nanoparticles and magnetic biosorbents for the wastewater treatment in recent 5 years (2017-2021). Among these materials, the development of magnetic biosorbents is attractive owing to their variable active sites, high specific surface area, easy separation and low cost. To improve the adsorption performance of biosorbents, the chemical activations such as acid, alkali and salt activations of biosorbents are discussed. In general, the oxidation reaction in acid, alkali and salt activations increases the porosity of biosorbents. The surface characteristics, surface chemistry of the biosorbents and magnetic biosorbents such as electrostatic interaction, π-π interaction and hydrogen bonding are highlighted. Ionic compounds are separated through ion exchange, surface charge and electrostatic interactions while the organic pollutants are removed via hydrophobicity, π-π interactions and hydrogen bonding. The effect of solution pH, adsorbent dosage, initial concentration of pollutants, adsorption duration and temperature on the adsorption capacity, and removal efficiency are discussed. Generally, an increase in adsorbent dosage resulted in a decrease in adsorption capacity due to the excessive active sites. On the other hand, a higher initial concentration or an increase in contact time of adsorbent increased the driving force, subsequently enhancing the adsorption capacity. Finally, this review will be concluded with a summary, challenges and future outlook of magnetic biosorbents. It is anticipated that this review will provide insights into engineering advanced and suitable materials to achieve cost-effective and scalable adsorbents for practical and sustainable environmental remediation.

Multidisciplinary Approach to Agricultural Biomass Ash Usage for Earthworks in Road Construction

Agricultural biomass has great bioenergy potential due to its availability, and it is a carbon-free energy source. During biomass incineration, biomass ash is formed, which is still considered as a waste without proper disposal and management solutions. Various biomass ash utilization options were investigated, mainly concerning engineering issues (the mechanical characterization of newly produced building materials or products), and there is a lack of knowledge of environmental issues arising from this “waste” material utilization in civil engineering practice. The main aim of this research is discussion of a different agricultural biomass characteristics as a fuel, the impact of agricultural biomass ashes (ABA) on the mechanical properties of stabilized soil with a particular emphasis on the environmental impacts within this kind of waste management. The results of this study indicate improved geotechnical characteristics of low-plasticity clay stabilized by lime/ABA binder. In addition to mechanical characterization for materials embedded in road embankments and subgrades, appropriate environmental risk assessment needs to be performed, and the results of this study indicate that the amount of ABAs added to the soil for roadworks should not have adverse effects on the soil fauna in the surrounding environment.

Agricultural waste management strategies for environmental sustainability

Globally, abundant agricultural wastes (AWs) are being generated each day to fulfil the increasing demands of the fast-growing population. The limited and/or improper management of the same has created an urgent need to devise strategies for their timely utilization and valorisation, for agricultural sustainability and human-food and health security. The AWs are generated from different sources including crop residue, agro-industries, livestock, and aquaculture. The main component of the crop residue and agro-industrial waste is cellulose, (the most abundant biopolymer), followed by lignin and hemicellulose (lignocellulosic biomass). The AWs and their processing are a global issue since its vast majority is currently burned or buried in soil, causing pollution of air, water and global warming. Traditionally, some crop residues have been used in combustion, animal fodder, roof thatching, composting, soil mulching, matchsticks and paper production. But, lignocellulosic biomass can also serve as a sustainable source of biofuel (biodiesel, bioethanol, biogas, biohydrogen) and bioenergy in order to mitigate the fossil fuel shortage and climate change issues. Thus, valorisation of lignocellulosic residues has the potential to influence the bioeconomy by producing value-added products including biofertilizers, bio-bricks, bio-coal, bio-plastics, paper, biofuels, industrial enzymes, organic acids etc. This review encompasses circular bioeconomy based various AW management strategies, which involve 'reduction', 'reusing' and 'recycling' of AWs to boost sustainable agriculture and minimise environmental pollution.

A Review on Bamboo as an Adsorbent for Removal of Pollutants for Wastewater Treatment

Water and wastewater treatment are very important for obtaining clean and sanitary water as well as protecting the environment from toxic pollutants. Not only enriched with cellulose and carbon but the abundant resources of bamboo also make it suitable to be utilized as an adsorbent. With the right processing technologies and improvements, the potential of bamboo is unlimited. This study review provides knowledge on the use of bamboo-based adsorbents for the removal of contaminants and pollutants in wastewater in the form of activated carbon, biochar, and aerogel. This review highlighted bamboo utilization and its relevance as an adsorbent for wastewater treatment. The technologies for the processing and improvement of bamboo as well as the performance of the bamboo-based adsorbents are also discussed in this study. The adsorption capacity of bamboo has shown improvement with modification and good adsorption capacity achieved with some of the adsorbent being able to be recycled and reused.

Adsorption Characteristics and Molecular Simulation of Malachite Green onto Modified Distillers’ Grains

Adsorbent material was prepared using distillers’ grains (DG), which is a waste product of distilleries. The DG was pre-treated with NaOH and esterification-modified with CS2, which is a commonly used anionic modifier. The structure and morphology of the adsorbent was characterized by FTIR, XRD, EDS, SEM, BET, and zeta potential. The related mechanism of adsorption of malachite green (MG) onto modified distiller’s grains (MDG) was studied by adsorption experiments and molecular simulation techniques. The experimental results showed that CS2 successfully modified the DG fiber, and simultaneously yielded the MDG with a uniform pore distribution. MDG had a considerable adsorption capacity of 367.39 mg/g and a maximum removal rate of 96.51%. After eight adsorption–desorption cycle experiments, the adsorption removal rate of MDG to MG dye remained at 82.6%. The adsorption process could be fitted well by a pseudo-second-order kinetic model (the correlation coefficient R2 > 0.998) and Freundlich isotherm adsorption equation (the correlation coefficient R2 > 0.972). Moreover, the adsorption of MG dye by MDG is a spontaneous, endothermic, and increased entropy process. The results of molecular simulation showed that the mechanism of MG molecules onto MDG was mainly chemical adsorption. The adsorption performance of MG onto MDG was better and more stable than DG. Molecular simulation also provided a theoretical guidance of MDG adsorption–desorption for the research on recycling of DG resources.

A review on adsorptive separation of toxic metals from aquatic system using biochar produced from agro-waste

Water is a basic and significant asset for living beings. Water assets are progressively diminishing due to huge populace development, industrial activities, urbanization and rural exercises. Few heavy metals include zinc, copper, lead, nickel, cadmium and so forth can easily transfer into the water system either direct or indirect activities of electroplating, mining, tannery, painting, fertilizer industries and so forth. The different treatment techniques have been utilized to eliminate the heavy metals from aquatic system, which includes coagulation/flocculation, precipitation, membrane filtration, oxidation, flotation, ion exchange, photo catalysis and adsorption. The adsorption technique is a better option than other techniques because it can eliminate heavy metals even at lower metal ions concentration, simplicity and better regeneration behavior. Agricultural wastes are low-cost biosorbent and typically containing cellulose have the ability to absorb a variety of contaminants. It is important to note that almost all agro wastes are no longer used in their original form but are instead processed in a variety of techniques to improve the adsorption capacity of the substance. The wide range of adsorption capacities for agro waste materials were observed and almost more than 99% removal of toxic pollutants from aquatic systems were achieved using modified agro-waste materials. The present review aims at the water pollution due to heavy metals, as well as various heavy metal removal treatment procedures. The primary objectives of this research is to include an overview of adsorption and various agriculture based adsorbents and its comparison in heavy metal removal.

Adsorptive Removal of Copper (II) Ions from Aqueous Solution Using a Magnetite Nano-Adsorbent from Mill Scale Waste: Synthesis, Characterization, Adsorption and Kinetic Modelling Studies

In this study, magnetite nano-adsorbent (MNA) was extracted from mill scale waste products, synthesized and applied to eliminate Cu²⁺ from an aqueous solution. Mill scale waste product was ground using conventional milling and impacted using high-energy ball milling (HEBM) for varying 3, 5, and 7 milling hours. In this regard, the prepared MNA was investigated using X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), field emission scanning electron microscopy-energy-dispersive X-ray spectroscopy (FESEM-EDS), UV-Vis spectroscopy, Fourier-transform infrared (FTIR), Brunauer-Emmett-Teller (BET) and zeta potential. The resultant MNA-7 h milling time displayed a crystalline structure with irregular shapes of 11.23 nm, specific surface area of 5.98 m²g^-1, saturation magnetization, Ms of 8.35 emug^-1, and isoelectric point charge at pH 5.4. The optimum adsorption capacity, q_e of 4.42 mg.g^-1 for the removal of Cu²⁺ ions was attained at 120 min of contact time. The experimental data were best fitted to the Temkin isotherm model. A comparison between experimental kinetic studies and the theoretical aspects showed that the pseudo-second-order matched the experimental trends with a correlation coefficient of (R² > 0.99). Besides, regeneration efficiency of 70.87% was achieved after three cycles of reusability studies. The MNA offers a practical, efficient, low-cost approach to reutilize mill scale waste products and provide ultra-fast separation to remove Cu²⁺ from water.

Engineered Magnetic Carbon-Based Adsorbents for the Removal of Water Priority Pollutants: An Overview

This review covers the preparation, characterization, and application of magnetic adsorbents obtained from carbon-based sources and their application in the adsorption of both inorganic and organic pollutants from water. Different preparation routes to obtain magnetic adsorbents from activated carbon, biochar, hydrochar, graphene, carbon dots, carbon nanotubes, and carbon nanocages, including the magnetic phase incorporated on the solid surface, are described and discussed. The performance of these adsorbents is analyzed for the removal of fluoride, arsenic, heavy metals, dyes, pesticides, pharmaceuticals, and other emerging and relevant water pollutants. Properties of these adsorbents and the corresponding adsorption mechanisms have been included in this review. Overall, this type of magnetic adsorbents offers an alternative for facing the operational problems associated to adsorption process in water treatment. However, some gaps have been identified in the proper physicochemical characterization of these adsorbents, the development of green and low-cost preparation methods for their industrial production and commercialization, the regeneration and final disposal of spent adsorbents, and their application in the multicomponent adsorption of water pollutants.

Enhanced biosorption of fluoride by extracted nanocellulose/polyvinyl alcohol composite in batch and fixed-bed system: ANN analysis and numerical modeling

The present investigation attempted to examine the defluoridation feasibility onto the extracted nanocellulose/PVA polymer composites. Nanocellulose were derived from sugarcane bagasse and blended with PVA (polyvinyl alcohol) polymer matrix. The defluoridation potential of nanocellulose/PVA was observed to be significantly dependent on the various operational factors including pH, time interval, etc. the Temkin isotherm (R² = 0.989) as well as the Langmuir isotherm equation (R² = 0.982) could well fit with the investigational data. Following the Langmuir isotherm, the maximum monolayer adsorption capacity for fluoride elimination at 25°C was obtained as 11.363 mg g^-1. The nature of rate-limiting steps involved in defluoridation process might be effectively predicted by pseudo-second-order kinetics. Values of thermodynamic state properties achieved as of the thermodynamic analysis showed that the defluoridation process was spontaneous, exothermic, and feasible. The diffusion and mass transfer study were estimated by following the Boyd's model. Average effective diffusion coefficient (D_e) at various initial fluoride concentrations (4-10 mg L^-1) was obtained as 15.3343×10^-7 m²s^-1 and the estimated magnitude of the mass-transfer coefficient (K_f) was 0.0346×10^-9 m s^-1 (temperature = 298 K, C₀= 6 mgL^-1). An ANN (artificial neural network) model applied to optimize and simulate the defluoridation procedure. Furthermore, continuous flow column reactor was conducted to investigate the practical applicability of composites in the defluoridation process. The Yoon-Nelson and the Thomas model exhibited excellent conformity with the breakthrough curves. Nanocellulose/PVA satisfactorily eliminated fluoride from its aqueous solution and can be considered as a suitable bio-sorbent for defluoridation.

Restoration of heavy metal-contaminated soil and water through biosorbents: A review of current understanding and future challenges

Heavy metal pollution in soil and water is a potential threat to human health as it renders food quality substandard. Different biosorbents such as microbial and agricultural biomass have been exploited for heavy metal immobilization in soil and sorptive removal in waters. Biosorption is an effective and sustainable method for heavy metal removal in soil and water, but the inherent challenges are to find cheap, selective, robust, and cost-effective bioadsorbents. Microbial and agricultural biomass and their modified forms such as nanocomposites and carbonaceous materials (viz., biochar, nanobiochar, biocarbon), might be useful for sequestration of heavy metals in soil via adsorption, ion exchange, complexation, precipitation, and enzymatic transformation mechanisms. In this review, potential biosorbents and their metal removal capacity in soil and water are discussed. The microbial adsorbents and modified composites of agricultural biomasses show improved performance, stability, reusability, and effectively immobilize heavy metals from soil and water. In the future, researchers may consider the modified composites, encapsulated biosorbents for soil and water remediation.

Effectiveness of a biogenic composite derived from cattle horn core/iron nanoparticles via wet chemical impregnation for cadmium (II) removal in aqueous solution

The objective of the current study was focused on the potential adsorption capability of a biogenic hydroxyapatite/iron nanoparticles-based composite tailored for the elimination of toxic pollutant, Cd(II) ions. Morphological along with physicochemical properties of composites were analyzed by different techniques including Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). It has been noticed an increase in cell parameters of prepared composites with an increase in the amount of nanoparticles. The best adsorbent was found to be the one with a 5% amount of nanoparticles (P₄₀₀F_e(5%)). The kinetics studies have shown that the pseudo-first-order-models were in good agreement for the removal of Cd(II) ions onto P₄₀₀Fe(5%) at any concentration, suggesting a physisorption mechanism. Besides, isotherms analysis has consistently revealed Freundlich as the model better explained the isotherm data, with a maximum removal capacity of 392.3 mg g^-1, higher compared to many adsorbents. Thermodynamically, the removal adsorption process of Cd(II) ions onto the composite favorable, exothermic, and spontaneous. The regeneration study has been also investigated with reusability used until four cycles. The overall results pointed out the suitability and efficiency of the prepared biogenic composite for the elimination of metal pollutants in wastewater.

Modeling and Optimization of Biochar Based Adsorbent Derived from Kenaf Using Response Surface Methodology on Adsorption of Cd2+

Cadmium is one of the most hazardous metals in the environment, even when present at very low concentrations. This study reports the systematic development of Kenaf fiber biochar as an adsorbent for the removal of cadmium (Cd) (II) ions from water. The adsorbent development was aided by an optimization tool. Activated biochar was prepared using the physicochemical activation method, consisting of pre-impregnation with NaOH and nitrogen (N2) pyrolysis. The influence of the preparation parameters—namely, chemical impregnation (NaOH: KF), pyrolysis temperature, and pyrolysis time on biochar yield, removal rate, and the adsorption capacity of Cd (II) ions—was investigated. From the experimental data, some quadratic correlation models were developed according to the central composite design. All models demonstrated a good fit with the experimental data. The experimental results revealed that the pyrolysis temperature and heating time were the main factors that affected the yield of biochar and had a positive effect on the Cd (II) ions’ removal rate and adsorption capacity. The impregnation ratio also showed a positive effect on the specific surface area of the biochar, removal rate, and adsorption capacity of cadmium, with a negligible effect on the biochar yield. The optimal biochar-based adsorbent was obtained under the following conditions: 550 °C of pyrolysis temperature, 180 min of heating time, and a 1:1 NaOH impregnation ratio. The optimum adsorbent showed 28.60% biochar yield, 69.82% Cd (II) ions removal, 23.48 mg/g of adsorption capacity, and 160.44 m2/g of biochar-specific area.

Assessment of agricultural waste-derived activated carbon in multiple applications

To minimize waste production and reduce reliance on fossil fuels, agricultural waste such as rice straw has been actively used in biochemical production. In Taiwan, cellulosic waste has been used in anaerobic digestion for bioethanol production. This process produces a large amount of biomass-associated sludge that may become a serious environmental issue. Therefore, in this study, the anaerobic digestion sludge was recycled for the production of activated carbon via pyrolysis and activation by KOH. Surface characterization showed increased surface area and development of microporous structure upon activation. The FTIR image showed that high temperature activation eliminated most functional groups in the activated carbon, except for CO and C-O groups. The results showed that the activated carbon could be used for pollutant adsorbents such as molecular dyes (methylene blue: 217 mg g^-1) and metal ions (copper: 169 mg g^-1) from aqueous solution. In addition, the as-synthesized activated carbon can be used for CO₂ capture and capacitor. Instead of focusing on one single application, we proposed that centralized production of activated carbon could be used in various applications, while further modification could be adopted depending on the need of its specific application.

Nickel aluminum layered double oxides modified magnetic biochar from waste corncob for efficient removal of acridine orange

The objective of this work was to use corncob as raw material to prepare green reusable magnetic biochar for removal of dyes in wastewater. For this purpose, an environmentally friendly NiAl layered double oxides modified magnetic corncob biochar (MC₁/NiAl-LDO) was obtained by pyrolysis of NiAl layered double hydroxides modified magnetic corncob biochar (MC₁/NiAl-LDH) at 700 °C for 3 h. The surface area of MC₁/NiAl-LDO is 552.62 m²·g^-1, which was much higher than that of MC₁ (26.83 m²·g^-1). MC₁/NiAl-LDO for acridine orange (AO) exhibited higher adsorption ability, the adsorption capacity of MC₁/NiAl-LDO was increased by 90% compared with MC₁. Adsorption experiments for AO on MC₁/NiAl-LDO were carried with effect of pH, adsorption time, initial concentrations of AO and ionic strength. MC₁/NiAl-LDO can be recycled nine times. The results exhibited that MC₁/NiAl-LDO was a low cost adsorbent, providing good example for th agricultural waste recycling.

Treatment of oil refinery effluent using bio-adsorbent developed from activated palm kernel shell and zeolite

This study investigated the potential of palm kernel shell (PKS) as a biomass feed for adsorbent production. This work aims at synthesizing green adsorbent from activated PKS by integrating iron oxide and zeolite. The newly developed adsorbents, zeolite-Fe/AC and Fe/AC, were analyzed for surface area, chemical composition, magnetic properties, crystallinity, and stability. The adsorbent efficiency in removing effluent from the palm oil mill was evaluated. The influence of operating parameters, including adsorbent dosage, H2O2, reaction time, and initial solution pH for adsorption performance was studied. The Fourier transform infrared analysis revealed that the adsorbents contain functional groups including OH, N-H, C[double bond, length as m-dash]O and C[double bond, length as m-dash]C, which are essential for removing pollutants. The SEM-EDX analysis shows holes in the adsorbent surface and that it is smooth. The adsorption study revealed that under optimized conditions, by using 4 g L-1 of adsorbent and 67.7 mM H2O2, zeolite-Fe/AC was able to remove 83.1% colour and 67.2% COD within 30 min. However, Fe/AC requires 5 g L-1 of adsorbent and 87.7 mM to remove 86.8 percent and 65.6 percent, respectively. This study also showed that zeolite-Fe/AC has higher reusability compared to Fe/AC. Among Freundlich and Temkin models, the experimental data were found to be best fitted with the Langmuir isotherm model. The kinetic analysis revealed that for both adsorbents, the adsorption process fitted the pseudo-second-order model (R 2 = 0.9724). The finding reflects monolayer adsorption of zeolite-Fe/AC and Fe/AC. This study thus demonstrates the applicability of low-cost green adsorbents produced from PKS to treat oil refinery effluent and other recalcitrant wastewaters.

Solid wastes from the enzyme production as a potential biosorbent to treat colored effluents containing crystal violet dye

Sugarcane bagasse, a largely available waste worldwide, was submitted to solid-state fermentation (SSF) using the fungus Metarhizium anisopliae, aiming to produce enzymes. The solid waste generated from SSF was tested as an alternative biosorbent to treat colored effluents containing crystal violet (CV) dye. The biosorbent, here named BW (bagasse waste), was characterized, and experimental tests were performed to verify the influence of pH and dosage on the CV biosorption. Isotherms and biosorption kinetics were performed, and the biosorption thermodynamic parameters were determined. The potential of BW was also evaluated for the treatment of a simulated textile effluent. The maximum biosorption capacity was 131.2 mg g^-1 at 328 K, and the Liu was the most appropriate model to represent equilibrium data. The biosorption was spontaneous and endothermic. The use of BW in the simulated effluent showed that it is an efficient material, reaching color removal values of 85%. Therefore, the sugarcane bagasse generated from SSF can be considered a potential biosorbent to remove CV from textile effluents. This finding is relevant from the total environment viewpoint, since, at the same time, SSF generates enzymes and a solid waste, which in turn can be used as biosorbent to treat colored effluents.

Compósitos en estado hidrogel con aplicación en la adsorción de metales pesados presentes en aguas residuales

La contaminación por metales pesados es un problema, que hoy en día no se ha logrado disminuir. Por esta razón, es necesario innovar constantemente las técnicas tradicionales con el fin de aplicar procesos eficientes que ayuden a remover los contaminantes e incluso recuperarlos para ser reincorporados a procesos productivos. En este contexto, la adsorción es una técnica tan versátil, que es viable su aplicación con materiales de diferentes características. Entre los materiales que han resultado adsorbentes eficientes, se encuentran las partículas inorgánicas y los polímeros/biopolímeros. Estos componentes por si solos presentan capacidades adsorbentes aceptables, pero en los últimos años se ha explorado la generación de matrices poliméricas en estado hidrogel reforzadas con materiales inorgánicos o mezclas de redes poliméricas generando compósitos, para mejorar o incrementar la capacidad de adsorción. Los hidrogeles compósitos conjugan una adsorción eficaz, buena área superficial específica y de fácil aplicabilidad, por lo que representan una gran alternativa para la disminución de los iones de metales pesados presentes en los ecosistemas acuáticos. Por este motivo, es la presente revisión de los materiales con propiedades adsorbentes, las estrategias para generar compósitos en estado hidrogel y sus propiedades adaptadas para la adsorción de iones de metales pesados, así como los retos y las áreas de oportunidad implícitos en esta generación de materiales innovadores. 

Low-cost sugarcane bagasse and peanut shell magnetic-composites applied in the removal of carbofuran and iprodione pesticides

In the present study, two agro-industrial wastes, sugarcane bagasse, and peanut shell were employed as support of magnetite nanoparticles for the synthesis of magnetic bio-composites: magnetic sugarcane bagasse (MB_O) and magnetic peanut shell (MPSo). The presence of magnetite was verified by Raman spectroscopy. Magnetic nanoparticles shape and size distribution were studied by TEM, while composites morphologies were observed by SEM. Structural characteristics of the pesticides and their possible chemical adsorption on composites were analyzed by FTIR. The removal was carried out by a batch adsorption process, and UV-VIS technique was used for pesticide concentration estimation. Elovich model described better all systems pointing out to a chemical adsorption process occurring. Experimental data isotherms of carbofuran and iprodione can be best explained by more than one mathematical model, but Sip was the ordinary equation in all systems. Maximum adsorption capacities of 175 and 89.3 mg/g for carbofuran, and 119 and 2.76 mg/g for iprodione, were obtained for MBo and MPSo, respectively.

Efficient Removal of Pb(II) from Aqueous Solutions by Using Oil Palm Bio-Waste/MWCNTs Reinforced PVA Hydrogel Composites: Kinetic, Isotherm and Thermodynamic Modeling

Polyvinyl alcohol (PVA) hydrogel are still restricted for some applications because their lower mechanical strength and thermal stability. The PVA-based composites are drawing attention for the removal of heavy metals based on their specific functionality in adsorption process. The main objective of this work is to synthesize oil palm bio-waste (OPB)/multiwalled carbon nanotubes (MWCNTs) reinforced PVA hydrogels in the presence of N,N′-methylenebisacrylamide (NMBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator via simple in-situ polymerization technique. The as-prepared reinforced nanocomposites were characterized by FESEM, BET surface area, differential scanning calorimetry (DSC), TGA and FTIR analysis. The possible influence of OPB and MWCNTs on the tensile strength, elongation at break and elastic modulus of the samples were investigated. It was found that reinforced nanocomposites exhibited enhanced mechanical properties as compared to non-reinforced material. The evaluation of reinforced nanocomposites was tested by the removal of Pb(II) aqueous solutions in a batch adsorption system. The pseudo-second-order kinetic model was used to illustrate the adsorption kinetic results and Langmuir isotherm was more suitable to fit the equilibrium results providing maximum adsorption capacities. The evaluation of thermodynamic parameters describes the spontaneous, endothermic and chemisorption adsorption process while activation energy reveals the physical adsorption mechanism. Therefore, the coordination effects among OPB, MWCNTs and PVA polymer hydrogels can produce a promising adsorbent material for wastewater treatment applications.

Critical review of magnetic biosorbents: Their preparation, application, and regeneration for wastewater treatment

The utilisation of magnetic biosorbents (metal or metal nanoparticles impregnated onto biosorbents) has attracted increasing research attention due to their manipulable active sites, specific surface area, pore volume, pore size distribution, easy separation, and reusability that are suitable for remediation of heavy metal(loid)s and organic contaminants. The properties of magnetic biosorbents (MB) depend on the raw biomass, properties of metal nanoparticles, modification/synthesis methods, and process parameters which influence the performance of removal efficiency of organic and inorganic contaminants. There is a lack of information regarding the development of tailored materials for particular contaminants and the influence of specific characteristics. This review focuses on the synthesis/modification methods, application, and recycling of magnetic biosorbents. In particular, the mechanisms and the effect of sorbents properties on the adsorption capacity. Ion exchanges, electrostatic interaction, precipitation, and complexation are the dominant sorption mechanisms for ionic contaminants whereas hydrophobic interaction, interparticle diffusion, partition, and hydrogen bonding are the dominant adsorption mechanisms for removal of organic contaminants by magnetic biosorbents. In generally, low pyrolysis temperatures are suitable for ionic contaminants separation, whereas high pyrolysis temperatures are suitable for organic contaminants removal. Additionally, magnetic properties of the biosorbents are positively correlated with the pyrolysis temperatures. Metal-based functional groups of MB can contribute to an ion exchange reaction which influences the adsorption capacity of ionic contaminants and catalytic degradation of non-persistent organic contaminants. Metal modified biosorbents can enhance adsorption capacity of anionic contaminants significantly as metal nanoparticles are not occupying positively charged active sites of the biosorbents. Magnetic biosorbents are promising adsorbents in comparison with other adsorbents including commercially available activated carbon, and thermally and chemically modified biochar in terms of their removal capacity, rapid and easy magnetic separation which allow multiple reuse to minimize remediation cost of organic and inorganic contaminants from wastewater.

As(III) and As(V) removal by using iron impregnated biosorbents derived from waste biomass of Citrus limmeta (peel and pulp) from the aqueous solution and ground water

Now a day's biosorbents with magnetic properties have been applied for water and wastewater treatment process, because of its magnetic nature it can be easily separated and can be reused more than one time. In the present study, two magnetic biosorbents were synthesized from waste biomass of Citrus limetta (peel and pulp) at 500 °C temperature represented as PAC-500 and PPAC-500. These biosorbents were effectively used for the removal of As(III) and As(V) from an aqueous solution and groundwater samples. The prepared biosorbents were characterized by using Brunauer Emmett Teller (BET), Zeta potential, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Disperssive X-ray (EDS), X-ray Diffraction (XRD) and Particle Size Analyzer (PSA). Isotherms, kinetics and thermodynamics were also applied to the obtained experimental data. The regeneration study revealed that the biosorbent can be recycled up to four cycles. The adsorbent capacity of PAC-500 and PPAC-500 for the sorption of As(III) was 714.28 μg/g and 526.31 μg/g, respectively, whereas the q_max value for As(V) sorption was 2000 μg/g for both the biosorbents (PAC-500 and PPAC-500). The effect of competitive ions was also studied that shows that the presence of H₂PO₄^- and CO₃² have negative effects on the sorption of As(III) and As(V). Arsenic is very toxic and it is a more important subject for consideration, therefore it is necessary to develop a low cost material that is very efficient in removing As from ground water contaminated with As water.

Nano-sized Prussian blue immobilized costless agro-industrial waste for the removal of cesium-137 ions

For human health and safety, it is of great importance to develop innovative materials with a vast capacity for powerful removal of radioactive ions from aqueous solutions. Prussian blue functionalized sugarcane bagasse (PB-SCB) was successfully prepared for the efficient elimination of radioactive cesium (¹³⁷Cs) using a nontoxic, environmentally friendly, and costless method. The prepared renewable material was characterized using different techniques to emphasize morphology, functional groups, crystal structure, and the adsorption process. The adsorption of Cs(I) was better fitted to the pseudo-second-order model than pseudo-first-order model which revealed a chemical adsorption mechanism. The experimental isotherm results were best illustrated by the Freundlich model (R² = 0.98). Besides, the obtained values for the thermodynamic parameters indicating that the adsorption process was endothermic and spontaneous in nature. In addition to demonstrating high adsorption capacity for Cs ion removal (56.7 mg/g at 30 °C), PB-SCB might consider being an efficient and cost-effective adsorbent for the decontamination of cesium, where an estimated cost analysis revealed that the expenditure for the removal of 1000 mg/L cesium from alkaline radioactive wastewater is likely to be US$0.12. Graphical abstract.

Activated Carbon from Prickly Pear Seed Cake: Optimization of Preparation Conditions Using Experimental Design and Its Application in Dye Removal

In the present study, the experimental design method was used to optimize the preparation conditions of an activated carbon from prickly pear seed cake by phosphoric acid activation. The parameters studied include impregnation ratio, carbonization temperature, and carbonization time. The optimal conditions for the preparation of the activated carbon with high adsorption capacity for methylene blue were identified to be an impregnation ratio of 2.9, carbonization temperature of 541°C, and carbonization time of 88 min. The obtained activated carbon was characterized by SEM/EDX, FTIR, pHpzc, and its capacity to adsorb methylene blue. FTIR analysis and pHPZC showed the acidic character of the activated carbon surface. The adsorption capacity of the optimal activated carbon was found to be 260 mg·g−1 for methylene blue. The adsorption equilibrium of methylene blue was well explained by the pseudo-second-order model and Freundlich isotherm. Furthermore, the performance of the produced activated carbon was examined by the methyl orange removal.

Adsorption of Methylene Blue and Pb2+ by using acid-activated Posidonia oceanica waste

Dead leaves of seagrass Posidonia oceanica were activated by using one mol L-1 acetic acid and used as an eco-adsorbent for the removal of methylene blue (MB) and Pb2+ from aqueous solutions. The seagrass was characterized by chemical and physical measurements that confirmed the acid-activation of seagrass. The favourable conditions for MB and Pb2+ adsorption onto the activated seagrass (SGa) were determined to be a pH range of 2-12 and ≥6, an adsorbent dosage of 3.0 and 0.5 g L-1, respectively, and a shaking time of 30 min, which are suitable for a wide range of wastewaters. The equilibrium data were analysed using the Langmuir, Freundlich and Dubinin-Raduskavich-Kaganer (DRK) adsorption isotherm models. The Freundlich and DRK models best describe the adsorption processes of MB and Pb2+, on SGa with capacities of 2681.9 and 631.13 mg g-1, respectively. The adsorption isotherm fitting and thermodynamic studies suggest that the adsorption mechanism of MB may combine electrostatic and physical multilayer adsorption processes, in which MB may be present as monomers as well as dimers and trimers which were confirmed from UV spectroscopy whereas Pb2+ is chemically adsorbed onto SGa. The pseudo-2nd-order kinetic model was utilized to investigate the kinetics of adsorption processes. The removal process was successfully applied for MB-spiked brackish waste water from Manzala Lake, Egypt, with removal efficiencies of 91.5-99.9%.

Novel combined method of biosorption and chemical precipitation for recovery of Pb2+ from wastewater

A novel combined biosorption-precipitation process has been designed and applied to recycle Pb²⁺ from low concentration lead containing wastewater. Pb²⁺ was firstly removed selectively from wastewater by pyromellitic dianhydride (PMDA) modified sugarcane bagasse (SB) fixed-bed column, and then, it was desorbed into the concentrated eluate and recycled by adding chemical precipitant. Adsorption performance of the column and optimum desorption and precipitation condition for Pb²⁺ were investigated in detail. Results showed that the as-prepared column could efficiently remove Pb²⁺ from aqueous solution and optimum condition for Pb²⁺ precipitation in eluate was at pH 3.0 and molar ratio of precipitant to Pb²⁺ of 5:1 by using Na₃PO₄ as precipitant. Recovery experiment illustrated that Pb²⁺ was selectively removed from wastewater containing ions of Pb²⁺, Zn²⁺, Cd²⁺, Ca²⁺, K⁺, and Na⁺ through competitive substitution adsorption on the modified SB, and mass ratio of the five metal ions in eluate was 96.8:0.7:0.7:0.7:0.5:0.5. Pb²⁺ in this concentrated and purified eluate solution was recycled efficiently by adding Na₃PO₄. The combined method had great potential in application of heavy metal recovery from wastewater.

Adsorption of heavy metal with modified eggshell membrane and the in situ synthesis of Cu-Ag/modified eggshell membrane composites

The objectives of this study were to remove heavy metals from wastewater through the biosorption method with modified biomass as an effective sorbent and to prepare metal/biomass composites with the same modified biomass as a direct template. Eggshell membrane (ESM) was selected and modified to adsorb heavy metals. Adsorption of metal ions on the modified ESM (MESM) might be attributed to electrostatic interaction, ion exchange and coordination effect with chelating ligands containing N and S on the surface of the MESM. The pH of the solution was a key factor affecting the adsorption. The Cu-Ag/MESM composites with uniform Cu-Ag NPs were prepared with MESM as matrices, and with Cu²⁺ and Ag⁺ adsorbed as metal sources. The Cu-Ag/MESM showed excellent catalytic performance in the reduction of 4-nitrophenol to 4-aminophenol in the aqueous phase. Because of the high stability of the Cu-Ag NPs supported on the macro-dimension supporter, Cu-Ag/MESM can be easily separated after the catalytic reaction and recycled.

Functionalized biochar derived from heavy metal rich feedstock: Phosphate recovery and reusing the exhausted biochar as an enriched soil amendment

This paper provides a circular win-win approach for recycling rhizofiltration biomass into multifunctional engineered biochar for various environmental applications (e.g. phosphate recovery) with a potential reuse of the exhausted biochar as an enriched soil amendment. Functionalized biochars were derived from the disposals of water hyacinth (Eichhornia crassipes) plants grown in synthetic contaminated water spiked with either Fe²⁺ (Fe-B), Mn²⁺ (Mn-B), Zn²⁺ (Zn-B) or Cu²⁺ (Cu-B) comparing with the original drainage water as a control treatment (O-B). The in-situ functionalization of biochar via the inherently heavy metal-rich feedstock produced homogenous organo-mineral complexes on biochar matrix without environmental hazards (e.g. volatilization or chemical sludge formation) associated with other post-synthetic functionalization methods. Physicochemical analyses (SEM-EDS, XRD, FTIR, BET and zeta potential (ζ)) confirmed the functionalization of Fe-B, Zn-B and Cu-B due to organo-mineral complexes formation, maximizing specific surface area, lowering the electronegativity, originating positively charged functional groups, and thus improving the anion exchange capacity (AEC) comparing with O-B. In contrary, physicochemical characteristics of Mn-B was in similarity with those of O-B. Phosphate recovery by the functionalized biochar was much greater than that of the unfunctionalized forms (O-B and Mn-B). Precipitation was the dominant chemisorption mechanisms for phosphate sorption onto biochar compared to other mechanisms (ion exchange, electrostatic attraction and complexation with active functional groups). The exhausted biochar showed an ameliorating effect on the low water and nutrient supply potentials of sandy soil, and thus improved fresh biomass yield and nutritional status of maize seedlings with some restrictions on its high micronutrient content.

Hydrothermal synthesis of hydrocalumite assisted biopolymeric hybrid composites for efficient Cr(vi) removal from water

Hydrocalumite (HC) incorporated biopolymer (alginate and chitosan) based hybrid composite materials were developed for the selective removal of chromium.