Remediation of water tainted with noxious hexavalent chromium using cetylpyridinium-modified bagasse biomass: adsorption and regeneration studies

Herein, cetylpyridinium-modified bagasse (SB-CPC) biomass was synthesized and applied for removal of noxious Cr(VI) ions from aqueous matrix. Batch mode analyses were conducted, and the results showed that SB-CPC adsorbent has a maximum uptake capacity (q_m) of 70.5 ± 3.2 mg g^-1 at 303 K. The adsorption isotherms and kinetics for elimination of Cr(VI) by SB-CPC were better fitted by Langmuir model and pseudo-second-order model, respectively. The occurrence of pseudo-second-order kinetic could be mainly influenced by the intra-particle diffusion mass transfer. Electrostatic attraction was the dominant underlying reaction mechanism followed by pore filing effect (minor). Thermodynamic study affirms the endothermic behavior and occurrence of physical adsorption process. SB-CPC adsorbent had exhibited an outstanding desorption-regeneration performance using NaOH solution; accordingly, it can practically be applied for remediation of wastewater tainted with Cr(VI) ions.

Enzymatic preparation of hydrophobic biomass with one-pot synthesis and the oil removal performance

Oil pollution is causing deleterious damage to aquatic ecosystems and human health. The utilization of agricultural waste such as corn stalk (CS) to produce biosorbents has been considered an ecofriendly and efficient approach for removing oil. However, most previous studies focused on the modification of the whole CS, which is inefficient due to the heterogeneity of CS. In this study, corn stalk pith (CP), which has excellent amphipathic characteristics, was selected to prepare a high-efficiency oil sorbent by grafting dodecyl gallate (DG, a long-chain alkyl) onto CP surface lignin via laccase mediation. The modified biomass (DGCP) shows high hydrophobicity (water contact angle = 140.2°) and superoleophilicity (oil contact angle = 0°) and exhibits a high oil sorption capacity (46.43 g/g). In addition, DGCP has good stability and reusability for adsorbing oil from the aqueous phase. Kinetic and isotherm models and two-dimensional correlation spectroscopy integrated with FTIR analyses revealed that the main sorption mechanism involves the H-bond effect, hydrophobic effect and van der Waals force. This work provides an ecofriendly method to prepare oil sorbents and new insights into the mechanisms underlying the removal of spilled oil from wastewater.

Removal of Chromium Species by Adsorption: Fundamental Principles, Newly Developed Adsorbents and Future Perspectives

Emerging chromium (Cr) species have attracted increasing concern. A majority of Cr species, especially hexavalent chromium (Cr(VI)), could lead to lethal effects on human beings, animals, and aquatic lives even at low concentrations. One of the conventional water-treatment methodologies, adsorption, could remove these toxic Cr species efficiently. Additionally, adsorption possesses many advantages, such as being cost-saving, easy to implement, highly efficient and facile to design. Previous research has shown that the application of different adsorbents, such as carbon nanotubes (carbon nanotubes (CNTs) and graphene oxide (GO) and its derivatives), activated carbons (ACs), biochars (BCs), metal-based composites, polymers and others, is being used for Cr species removal from contaminated water and wastewater. The research progress and application of adsorption for Cr removal in recent years are reviewed, the mechanisms of adsorption are also discussed and the development trend of Cr treatment by adsorption is proposed.

Study on adsorption of hexavalent chromium by composite material prepared from iron-based solid wastes

A new adsorbent with chromium removal function was synthesized by carbon thermal method using iron-containing waste Fenton sludge and carbon-containing solid waste fly ash to treat high pH scoring wastewater generated from industrial processes. The results showed that the adsorbent used T = 273.15 K, pH = 10, t = 1200 min, C₀ = 100 mg/L, had a removal rate of Cr(VI) of more than 80%, and the adsorption capacity could reach 393.79 mg/g. The characterization results show that the synthesized mesoporous nitrogen-doped composite material has a large specific surface area and mesoporous structure, and the surface of the material is rich in oxygen-containing functional groups and active sites. Compared with other studies, the adsorption capacity of the material is larger, which indicates that the removal effect of Cr(VI) in this study is better. The adsorption kinetic results show that the adsorption follows a pseudo second kinetic model, and the adsorption process is a chemisorption involving electron sharing or electron exchange. This experiment designed a simple method to synthesize mesoporous nitrogen-doped composites using industrial solid waste, with raw materials from cheap and easily available industrial solid waste, and solved the dual problems of heavy metals in wastewater and solid waste, providing a new idea for the resource utilization of Fenton sludge while not producing secondary pollution.

Biocomposite based on zirconium and amine-grafted walnut shell with antibacterial properties for the removal of Alizarin red in water: batch and column studies

Recent progress has been made in the application of novel zirconium-loaded amine-grafted walnut shells as multifunctional adsorbents for the remediation of Alizarin red (AR) and bacteria in aqueous solutions. The morphology and functional groups of ACWNS@Zr were studied using Brunauer-Emmett-Teller (BET) techniques, X-ray diffraction (XRD), pH point of zero charges (pHpzc), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. Adsorption and regeneration tests were carried out in batch and column mode. The ACWNS@Zr had a Langmuir maximum capacity of 415.5 ± 6.1 mg g^-1 at 303 K. The spread plate technique was used to evaluate the adsorbent's antimicrobial properties against Staphylococcus aureus and Escherichia coli. ACWNS@Zr exhibited inhibitory potential towards S. aureus and E. coli in the suspensions by 53.3% and 15.0%, respectively. Electrostatic interaction and complexation interaction could be the key mechanisms governing AR dye removal. Equilibrium isotherms fit Langmuir models better for both batch and column studies, while adsorption kinetics to pseudo-second-order and Thomas models for batch and column studies, respectively. Thermodynamic studies indicated that the adsorption process was endothermic and spontaneous. Furthermore, columns' mass transfer capacity (B) increased as the concentration increased due to the enhanced driving force for AR adsorption onto ACWNS@Zr. Regeneration with NaOH solution of AR-loaded ACWNS@Zr was remarkable.

Reduced cadmium (Cd) accumulation in lettuce plants by applying KMnO4 modified water hyacinth biochar

In this study, water hyacinth was adopted to prepare biochar followed by modification using KMnO₄. And the modified biochars were applied in Cd contaminated soil, exploring the effects of water hyacinth biochar on lettuce growth, Cd enrichment, soil enzyme activities and microbial changes by pot experiments. Modified biochar application significantly reduced the Cd accumulation in lettuce shoots and roots. Compared to the control, the application of water hyacinth biochar at 1% rate resulted in significant reduction of Cd contents by 40.7% and 33.7% in the shoots and roots of lettuce. Also, the reduction was 33.3% and 20.8% compared with the application rate of unmodified biochar. With the increase of biochar application, the amount of Cd was absorbed by lettuce shoots and roots showing significant reduction of plant Cd accumulation in response to the biochar application rate. Additionally, the lowest available Cd concentration in soil (1.34 mg kg⁻¹) was obtained with the application of modified biochar at 1% rate, which might be the main reason for the lower Cd concentration in lettuce shoot and root parts. Furthermore, structural analysis showed that Cd was fixed on the modified biochar, in a passivated state, by larger specific surface area, more active sites and more stable covalent binding complexes leading to a strong decrease of the available Cd in the soil. Moreover, it was concluded that the increment of the enzyme activities in the soil was up to 2.51 times significantly following the application of modified water hyacinth biochar with 3% amount. Lastly, 16sRNA sequencing showed that biochar addition may lead to changes of microbial structure and abundance in soil.

Recent developments in alginate-based adsorbents for removing phosphate ions from wastewater: a review

The huge development of the industrial sector has resulted in the release of large quantities of phosphate anions which adversely affect the environment, human health, and aquatic ecosystems. Naturally occurring biopolymers have attracted considerable attention as efficient adsorbents for phosphate anions due to their biocompatibility, biodegradability, environmentally-friendly nature, low-cost production, availability in nature, and ease of modification. Amongst them, alginate-based adsorbents are considered one of the most effective adsorbents for removing various types of pollutants from industrial wastewater. The presence of active COOH and OH^- groups along the alginate backbone facilitate its physical and chemical modifications and participate in various possible adsorption mechanisms of phosphate anions. Herein, we focus our attention on presenting a comprehensive overview of recent advances in phosphate removal by alginate-based adsorbents. Modification of alginate by various materials, including clays, magnetic materials, layered double hydroxides, carbon materials, and multivalent metals, is addressed. The adsorption potentials of these modified forms for removing phosphate anions, in addition to their adsorption mechanisms are clearly discussed. It is concluded that ion exchange, complexation, precipitation, Lewis acid-base interaction and electrostatic interaction are the most common adsorption mechanisms of phosphate removal by alginate-based adsorbents. Pseudo-2^nd order and Freundlich isotherms were figured out to be the major kinetic and isotherm models for the removal process of phosphate. The research findings revealed that some issues, including the high cost of production, leaching, and low efficiency of recyclability of alginate-based adsorbents still need to be resolved. Future trends that could inspire further studies to find the best solutions for removing phosphate anions from aquatic systems are also elaborated, such as the synthesis of magnetic-based alginate and various-shaped alginate nanocomposites that are capable of preventing the leaching of the active materials.

Facile synthesis of Fe3O4 anchored polyaniline intercalated graphene oxide as an effective adsorbent for the removal of hexavalent chromium and phosphate ions

Adsorption media of hybrid composites is a promising candidate to eliminate the toxic contaminants from an aqueous environment, and good regeneration ability has received considerable interest to be utilized in water and wastewater treatment. Herein, we synthesized Fe₃O₄ anchored polyaniline intercalated graphene oxide (Fe₃O₄x%-PANI@GO, where x = 10, 20 and 50% of Fe₃O₄ particles) hybrid composites by co-precipitation and modified Hummers' method, followed by in-situ polymerization. The as-synthesized Fe₃O₄x%-PANI@GO acts as a potential host in welcoming the guest ions such as anionic contaminants with different interactions in this work. Besides, the advantages of easy separation by the external magnetic field, the Fe₃O₄x%-PANI@GO hybrid composite also achieve a great adsorption efficiency of 143.54 and 135.67 mg/g for Cr(VI) and phosphate ions, respectively, than the other adsorbents reported in the literature. The as-synthesized adsorbents were characterized by different analytical techniques and influencing parameters such as contact time, co-existing anions, solution pH, adsorption isotherms, and kinetics were studied in detail. The adsorption system of Fe₃O₄50%-PANI@GO hybrid composite follows the Langmuir isotherm and pseudo-second-order kinetic model for the elimination of Cr(VI) and phosphate ions from aqueous solutions. The feasible removal mechanism of Cr(VI) and phosphate ions was explored by FTIR and XPS techniques for anionic pollutants. Moreover, the selectivity and recyclability tests showed that the Fe₃O₄50%-PANI@GO hybrid composites demonstrated a high adsorption capacity towards the anionic ions from the aqueous environment. Therefore, the present investigation suggested that the Fe₃O₄50%-PANI@GO hybrid composites is an effective adsorbent for the elimination of Cr(VI) and phosphate ions from wastewater.

Development of triaminotriazine functionalized graphene oxide capped chitosan porous composite beads for nutrients remediation towards water purification

The porous, definite and nitrogen rich triaminotriazine (TAT) grafted graphene oxide (GO) known as TATGO composite was developed for nutrients (NO₃^- and PO₄^3-) retention. Additionally, the structural property of TATGO composite was improved with the use of chitosan (CS) to produce easily separable TATGO@CS hybrid beads which possess the significant NO₃^- and PO₄^3- adsorption capacities of 58.46 and 61.38 mg/g respectively than their individual materials. The instrumentations such as SEM, TGA, FTIR, EDAX, XRD and BET studies were executed for adsorbents. The optimization of the parameters accountable for adsorption process was performed in batch scale. The effect of isotherms (Langmuir, Freundlich and Dubinin-Radushkevich (D-R)), kinetics (pseudo-first/second order and particle/intraparticle diffusion) and thermodynamic parameters (ΔG°, ΔH° and ΔS°) of the adsorption was explored. The removal mechanism of TATGO@CS hybrid beads was to be electrostatic attraction on NO₃^- and PO₄^3-. The field applicability and reuse of TATGO@CS hybrid beads was also inspected.

Biosorption of methylene blue and malachite green on biodegradable magnetic Cortaderia selloana flower spikes: modeling and equilibrium study

This study involves the production of a novel biosorbent obtained from Cortaderia selloana flower spikes (CSFs). Magnetic C. selloana flower spikes (nM∞CSFs) was applied as an ideal biosorbent for the elimination of dyes from water. They were utilized for the removal from aqueous solutions of malachite green (MG) and methylene blue (MB) dyes. The analyses of the equilibrium were done under certain experimental parameters such as contact time, initial dye concentration, pH, and quantity of biosorbent. The rapid intake of dyes to reach the equilibrium in a short period time showed the effectiveness of nM∞CSFs to adsorb MG and MB. The experimental information of MB and MG was obtained from the Langmuir model and it confirmed the magnificent dye biosorption ability; 72.99 mg/g for CSFs/MB, 119.05 mg/g for nM∞CSFs/MB, 31.06 mg/g for CSFs/MG, and 56.50 mg/g for nM∞CSFs/MG. Langmuir's model affirmed the excellent dye biosorption ability. The pseudo-second-order kinetic model displayed a great fit to the experimental result for the removal of MG and MB. The nM∞CSFs compared with raw biosorbent affirmed that the magnetic form of the biosorbent has a greater removal ability for MB and MG. nM∞CSFs is a noteworthy biosorbent for MB and MG removal from wastewater. [Figure: see text] HIGHLIGHTS Magnetic Cortaderia selloana flower spikes (nM∞CSFs) was synthesized for the biosorption of dyes FT-IR and SEM analysis were used for characterization. The Langmuir isotherm model fitted the data of the adsorption for nM∞CSFs nM∞CSFs is a noteworthy biosorbent for MB and MG removal from wastewater. A NOVELTY STATEMENT   This novel biodegradable biosorbent (magnetic-C. selloana flower spikes-(nM∞CSFs)) has many different functional groups to bind MG and MB from aqueous medium. The method to bring the magnetic form was well described and gives an astronomically immense capacity for the abstraction of the dyes. It resists in acidic or basic medium and has a vigorous structure. It has an immense capacity for the dyes compared to other biosorbents. It can be cited by a sizably voluminous number of investigators or researchers when it is published because it is incipient biosorbent in the literature and can be utilized as a novel biosorbent for the removal of dyes.

Preparation, Characterization, and Application of Novel Ferric Oxide-Amine Material for Removal of Nitrate and Phosphate in Water

Ferric oxide-amine material was synthesized and applied as a novel adsorbent for nitrate and phosphate removal from aqueous solution. The properties of ferric oxide-amine were examined using TGA, FTIR, BET, SEM, EDX, SEM-mapping, and XRD analysis. The results showed that the adsorption using ferric oxide-amine material reached equilibrium after 30 and 60 min for nitrate and phosphate, respectively. The highest nitrate and phosphate adsorption capacities were 131.4 mg nitrate/g at pH 5-6 and 42.1 mg phosphate/g at pH 6. The effects of adsorbent dosage, initial concentrations of nitrate and phosphate, and adsorption temperature were also investigated. Among the three adsorbents of ferric oxide-amine, ferric oxide, and Akualite A420 ion exchange resin, ferric oxide-amine material had the highest adsorption capacity for nitrate and phosphate removal. These results suggest a great potential use of ferric oxide-amine material for water treatment in practical applications.

Fabrication and evaluation of a regenerable HFO-doped agricultural waste for enhanced adsorption affinity towards phosphate

Chemical modification of agricultural waste biomass has proved to be an economy and effective approach to capture phosphate ions, except for that under acidic conditions and highly competitive ion systems. According to this, a new nanocomposite (HFO@St+) was fabricated by incorporating nano-sized hydrous Fe(III) oxides (HFO) within aminated wheat straw in order to overcome the bottleneck. The optimal pH of phosphate uptake by HFO@St+ was greatly broadened and observed over a wide pH range between 2.0 and 7.0. The binary exchange reaction indicated that phosphate was strongly and preferably adsorbed by HFO@St+ with the separation factor K of phosphate over nitrate increasing from 0.23-1 or 0.20-0.26 to 2.5-38 or 2.5-15 for near neutral or acidic pHs, respectively. The sorption selectivity for HFO@St+ followed the order of phosphate > nitrate > chloride under experimental conditions. The presence of inorganic and organic ligands (SO₄ and HA) showed no significant effect on phosphate adsorption. XPS and FT-IR analyses were performed to explore the underlying mechanism of adsorption. The exhausted material could be regenerated with NaOH-NaCl solution for at least ten cycles, indicating that HFO@St+ can be used as a sustainable biomass product with excellent adsorption affinity for phosphate removal.

Flow-induced crystallization of biochar in bio-asphalt under various aging conditions

Flow-induced crystallization (FIC) in polymers is an important problem that occurs on a very rapid time scale. This study aims to evaluate the flow-induced crystallization of bio-asphalt modified with different contents of biochar under various aging conditions. Small angle X-ray scattering and molecular dynamic simulations were performed to impose extensional deformation and the nucleation process. The rheological properties were measured using the dynamic shear rheometer (DSR) and the morphology of biochar modified bio-asphalt (BMBA) was measured using an optical microscope. The relative scattering intensity during crystallization appeared to peak at four strain rates: 13.2 s^-1, 19.6 s^-1, 25.4 s^-1, and 27.3 s^-1. The results showed that the addition of biochar could improve the flow-induced crystallization and enhance the high-temperature properties of bio-asphalt. Moreover, crystallization status of BMBA is lamellar crystals. Ultraviolet and pressure aging vessel aging could remarkably affect the crystallization status of BMBA and promote the formation of crystals.

Efficient phosphate accumulation in the newly isolated Acinetobacter junii strain LH4

Phosphate (PO₄^3-) accumulation associated with bacteria contributes to efficient remediation of eutrophic waters and has attracted attention due to its low cost, high removal efficiency and environmental friendliness. In the present study, we isolated six strains from sludge with high concentrations of chemical oxygen demand, total nitrogen and total phosphorus levels. Among them, strain LH4 exhibited the greatest PO₄^3- removal ability. Strain LH4 is typical of Acinetobacter junii based on physiological, biochemical, and molecular analyses and is a PO₄^3--accumulating organism (PAO) based on toluidine blue staining. The strain grew quickly when subjected to aerobic medium after pre-incubation under anaerobic condition, with a maximum OD₆₀₀ of 1.429 after 8 h and PO₄^3- removal efficiency of 99%. Our data also indicated that this strain preferred utilizing the carbon (C) sources sodium formate and sodium acetate and the nitrogen (N) sources NH₄Cl and (NH₄)₂SO₄ over other compounds. To achieve optimal PO₄^3- removal efficiency, a C:N ratio of 5:1, inoculation concentration of 3%, solution pH of 6, incubation temperature of 30 °C, and shaking speed of 100 rpm were recommended for A. junii strain LH4. By incubating this strain with different concentrations of PO₄^3-, we calculated that its relative PO₄^3- removal capacity ranged from 0.67 to 3.84 mg L^-1 h^-1, ranking in the top three among reported PAOs. Our study provided a new PO₄^3--accumulating bacterial strain that holds promise for remediating eutrophic waters, and its potential for large-scale use warrants further investigation.

Magnetically Modified Agricultural and Food Waste: Preparation and Application

The annual food and agricultural waste production reaches enormous numbers. Therefore, an increasing need to valorize produced wastes arises. Waste materials originating from the food and agricultural industry can be considered as functional materials with interesting properties and broad application potential. Moreover, using an appropriate magnetic modification, smart materials exhibiting a rapid response to an external magnetic field can be obtained. Such materials can be easily and selectively separated from desired environments. Magnetically responsive waste derivatives of biological origins have already been prepared and used as efficient biosorbents for the isolation and removal of both biologically active compounds and organic and inorganic pollutants and radionuclides, as biocompatible carriers for the immobilization of diverse types of (bio)molecules, cells, nano- and microparticles, or (bio)catalysts. Potential bactericidal, algicidal, or anti-biofilm properties of magnetic waste composites have also been tested. Furthermore, low cost and availability of waste biomaterials in larger amounts predetermine their utilization in large-scale processes.

Comparative analysis on adsorption properties and mechanisms of nitrate and phosphate by modified corn stalks

We compare and analyze the different properties and mechanisms of MCS on nitrate and phosphate.

Facile synthesis of tea waste/Fe3O4nanoparticle composite for hexavalent chromium removal from aqueous solution

A tea waste/Fe₃O₄composite was prepared through chemical co-precipitation approach and was used for Cr(vi) removal, involving an adsorption-coupled reduction mechanism.