Reusable Adsorbent Research Articles

Transforming Food Biowaste into Selective and Reusable Adsorbents for Pesticide Removal from Water

With growing concerns regarding environmental pollution and the need for sustainable waste management practices, this study investigates the potential of utilizing spent coffee grounds (SCG) as a precursor for producing functional carbon materials aimed at organophosphorus pesticide remediation under environmentally relevant conditions. Carbonization of SCG is followed by various activation methods, including treatment with potassium hydroxide, phosphoric acid, and carbon dioxide, individually or in combination. The resulting biochars are systematically analyzed for their adsorption performance towards malathion and chlorpyrifos. Screening tests revealed a selective adsorption preference towards aromatic chlorpyrifos over aliphatic malathion. Activation processes significantly influence adsorption kinetics and efficiency, with physical activation showing notable adsorption rates and capacity enhancements. Moreover, the SCG-derived biochars exhibit a pronounced dependency on adsorption temperature. Adsorption, regeneration, and reuse of the most promising material are tested in a real, spiked tap water sample, proving that the presence of ions in tap water did not affect the adsorption and that the material has the potential to be reused more than ten times. This work proposes a straightforward approach for recycling SCG by converting it into functional carbon materials, underscoring the importance of selecting the appropriate activation processes and conditions for practical applications in pesticide remediation.

Fabrication and adsorption characteristics of cuprammonium cellulose-based membranes for removing anionic and cationic dyes

A cotton linter-based source was used to form conjugate electrospun membranes composed of cuprammonium cellulose, polyethylene oxide, and polyacrylonitrile for the removal of the anionic and cationic dyes from aqueous media. The highest removal efficiencies of 94 %, 89.9 %, 87.4 % were achieved for the anionic dyes Congo red (CR), Metanil yellow (MY), and Methyl orange (MO), respectively, and less so on the cationic dyes Crystal violet (CV), and Rhodamine B (RB) were 55.8 % and 15.1 %, respectively. The pseudo-second-order model effectively described the adsorption kinetics for both types of dyes. The composite membrane exhibited adsorption behaviors following the Dubinin-Radushkevich (D-R) isothermal model. Thermodynamics study suggests that the adsorption process was spontaneous except for the RB dye. The activation energy values of CR, MY, MO, CV, and RB dyes were 27.65, 21.17, 11.50, 10.47, and 71.12 kJ/mol, respectively, confirming the physisorption phenomenon for CR, MY, MO, and CV dyes, while chemisorption occurs for RB dyes. This study investigates the potential of a conjugate electrospun membranes as a reusable adsorbent for dye removal. The effects of solution pH, temperature, and dye concentration on adsorption performance were systematically evaluated. The conjugate electrospun membrane efficiency declined by only 10 % after undergoing five adsorption/desorption cycles.

Copper-saturated chitosan beads (CuSCBs) for Enhanced phosphate removal

This study investigates the sequential use of non-cross-linked chitosan beads (CBs) for copper and phosphate adsorption, emphasizing copper site saturation and selective phosphate binding. Initially, CBs were loaded with copper until saturation was achieved, where all available sites were occupied by copper at an initial concentration of 100 mg/L. These copper-saturated chitosan beads (CuSCBs) were subsequently applied for phosphate adsorption, achieving a maximum adsorption capacity of 85.89 mg/g at pH 5. X-ray Photoelectron Spectroscopy (XPS) analysis revealed a shift in the Cu2O binding energy to lower values upon phosphate adsorption, indicating that phosphate ions interact primarily with the copper ions intercalated on the CBs rather than the chitosan matrix. Additionally, the nitrogen spectra showed no shift, confirming that the amine groups of chitosan do not participate in phosphate binding. The findings suggest a 1:1 interaction ratio between copper and phosphate ions, with each phosphate ion binding to one copper ion, creating a stable and selective adsorption site. The adsorption data fit the Langmuir isotherm and pseudo-second-order kinetic models, suggesting a homogeneous monolayer adsorption mechanism driven by chemisorption, where each copper site on the chitosan surface selectively binds one phosphate ion. Furthermore, the CuSCBs demonstrated minimal copper leaching and retained 90 % of their phosphate adsorption capacity over multiple adsorption–desorption cycles, highlighting their potential as effective and reusable adsorbents for water treatment applications targeting copper and phosphate removal.

Investigation of the biological removal of nickel and copper ions from aqueous solutions using mixed microalgae

AbstractThe use of mixed microalgae offers an effective solution for the management of contamination risks in cultivation while enhancing economic viability. In this study, mixed microalgae were used for the first time for the removal of copper (Cu) and nickel (Ni) from aqueous solutions. The characteristics of the adsorbents were examined thoroughly, and the adsorption process was assessed using isotherms, kinetics, and thermodynamics. Particle size, concentration, contact time, temperature, and pH were among the variables assessed. The findings demonstrated that, at an initial concentration of 100 mg L–1 and a pH of 6, the maximum adsorption of Cu with a particle size of 1 mm (90.20%) took place in 60 min. The highest adsorption rate (78.25%) was found for Ni. Microalgae performed best over 180 min at room temperature and at pH values that promoted metal dissolution. The removal percentages of wet and dried microalgae were comparable, and the wet adsorbent was more economical. It was feasible to remove both metals at the same time. Up to three cycles of adsorbent reuse were possible, with sodium hydroxide treatment offering superior removal to hydrochloric acid. Thermodynamic analysis demonstrated that this process, which results in a disordered state, is exothermic and spontaneous.

Separation of molybdenum and tungsten using selective adsorption with zirconium based metal organic framework

BackgroundThe separation of tungsten and molybdenum has always been a significant challenge. Metal organic frameworks (MOFs) has potential to solve the problem. In this study, the adsorption and separation performance of UiO-66 for tungsten and molybdenum and adsorption mechanism were investigated. MethodsUiO-66 was synthesized by solvothermal method. The physical and chemical properties of UiO-66 and adsorption mechanism were characterized and analyzed by XRD, SEM-EDS, FT-IR, Zeta-potential, XPS and thermodynamic analysis, the adsorption and separation performance of Mo/W using UiO-66 were evaluated by ICP-OES. Significant findingsUiO-66 with uniform pore size could be obtained under the conditions of crystallization for 24 h at 180 °C. This study revealed superior Mo/W separation performance under acidic conditions, where the adsorption capacity for Mo (QMo) of UiO-66 was 219.4 mg⋅g−1 and the highest separation factor (βMo/W) was 52.3. It was found that the mechanism involved the effect of pore size, electrostatic attraction and the metal point Zr had stronger affinity for Mo. This material was expected to serve as an eco-friendly and reusable adsorbent for separation of tungsten and molybdenum in resource recovery, aiming for high-quality regeneration of both metals.

Synthesis and characterization of allyl mannitol cross-linker based novel hydrogel for capturing of toxic metal ions from aqueous solution

ABSTRACT Three grades of allyl-mannitol cross-linker-based hydrogel (AMCLHs hydrogel) have been synthesized with the help of acrylic acid and acrylamide monomers using a free radical co-polymerization technique. The three prepared grades of AMCLHs hydrogel have been referred to as AMCLHs-1, AMCLHs-2, and AMCLHs-3, respectively. The prepared AMCLHs hydrogels have been characterized by several analytical techniques viz. Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG) analysis, point of zero charge (ΔpHPZC), analysis, and scanning electron microscope (SEM) analysis, respectively. The synthesized hydrogels have been utilized for the elimination of Cu2+ and Co2+ ions from wastewater. The properties of prepared AMCLHs hydrogels, i.e. swelling and water retention ratio have been studied in distilled water under optimized conditions. The maximum swelling ratio of the best grade of hydrogel (AMCLHs-1) has been found to be 400.5 g/g with the water retention ratio of 75.09% during 24 h. These findings indicate the AMCLHs-1 hydrogel has remarkable swelling and water retention capacity. The maximum metal ion removal efficiency of AMCLHs-1 hydrogel from aqueous solutions has been found to be 96.6% for Cu2+ and 94.2% for Co2+ ions under optimum conditions. The experimental data fitted well with the Langmuir and Freundlich adsorption models, revealing maximum adsorption capacities of 431.03 mg/g for Cu2+ ions and 414.93 mg/g for Co2+ ions, respectively. In addition, the rate for the adsorption of Cu2+ and Co2+ ions onto AMCLHs-1 hydrogel follows both Pseudo first and second-order kinetic models. The negative ΔG values indicate that the adsorption process occurs spontaneously, while positive ΔH values suggest that the adsorption process is exothermic in nature. The prepared AMCLHs hydrogel is reusable and exhibits high desorption efficiency with 87.63% for Cu2+ and 85.21% for Co2+ metal ions even after the fourth cycle. Overall, AMCLHs hydrogel is a cost-effective and reusable adsorbent that possesses a significant potential for heavy metal ion removal from aqueous solutions.

Revolutionizing waste: Harnessing agro-food hydrochar for potent adsorption of organic and inorganic contaminants in water.

Constant pollution from a wide range of human activities has a negative impact on the quantity and quality of the planet's water resources. On the other hand, agro-food waste can impact climate change and other forms of life, in addition to having social, economic, and environmental consequences. However, as a result of their inherent physicochemical properties and lignocellulosic composition, these residues are becoming increasingly recognized as valuable products in line with government policies advocating zero waste and circular economies. An advantageous way to convert these wastes into energy and chemicals is hydrothermal carbonization (HTC). This review highlights the valorization of agro-food waste into hydrochar-based adsorbents for the elimination of organic and inorganic contaminants from aqueous environments. An overview of the toxicity of pollutants in aqueous environments, food waste management, as well as HTC technology was initially proposed. Then, a discussion on the conversion of major agro-food wastes into contaminant adsorbents was given in detail. Adsorption mechanisms as well as the possibility of reuse of adsorbents were also discussed. Enhanced properties of the produced materials enable them to provide competent solutions to various ecological contexts, including removing pollutants from wastewater with cost-effectiveness and satisfactory results. Besides addressing environmental concerns, this sustainable approach opens the door for more environmentally-friendly and resource-efficient applications in the future, making it an exciting prospect.

Enhancing Environmental Remediation: Advancements in Chemically Crosslinked Cyclodextrin‐Based Materials for Organic and Inorganic Pollutant Removal

AbstractConcern over the harmful impacts of pollutants on human health and the environment has increased in recent decades due to their widespread presence in water resources. These pollutants include pesticides, poisonous textile dyes, and micropollutants. It is essential to remove these pollutants from wastewater to enhance the quality of water for industrial usage. Because of externally hydrophilic and internally hydrophobic qualities, cyclodextrin and its derivatives have shown great promise as adsorbents for the treatment of wastewater. While cyclodextrins cannot be used as adsorbents on their own due to their water solubility, they can be efficiently polymerized with different types of cross‐linkers to increase their stability and effectiveness. This review article examines chemically crosslinked materials based on cyclodextrin and its derivatives, utilizing various cross‐linkers such as epichlorohydrin, glutaraldehyde, citric acid, N,N′‐methylene bisacrylamide and maleic anhydride. These materials are evaluated for their effectiveness in adsorbing textile dyes, micropollutants, pharmaceuticals, and pesticides from wastewater. Additionally, this article provides a detailed explanation of adsorption kinetics, thermodynamics, and kinetic isotherms for the removal of contaminants. It also discusses the mechanism of contaminant adsorption, and reusability of adsorbents. Finally, this study delves into the challenges and exciting future prospects of CD‐based adsorbents, highlighting their potential to revolutionize wastewater treatment.

Evaluating the efficacy of palm waste in adsorption processes for wastewater treatment: A review

AbstractThe growing environmental concerns related to industrial effluents and waste underscore the urgent need for sustainable and cost‐effective wastewater treatment solutions. This review investigates the efficacy of palm waste‐derived adsorbents for removing heavy metals and organic pollutants from wastewater. It explores various modifications—including physical, chemical, and nanomaterial enhancements—applied to palm waste materials such as palm kernel shells, empty fruit bunches, and palm oil fuel ash, aimed at improving their adsorption capacities. The review reveals that these modified palm waste adsorbents demonstrate high removal efficiencies for contaminants like Cu(II), Pb(II), and organic dyes, often surpassing conventional adsorbents. Nonetheless, challenges remain, such as optimizing adsorbent preparation, understanding adsorption mechanisms in multi‐component systems, and enhancing adsorbent reusability. This review highlights the need for continued research to address these issues and advance the application of palm waste‐based materials in sustainable wastewater treatment.

Waste glass as a source for green synthesis of mesoporous adsorbent for efficient removal of heavy metals

Mesoporous analcime Adsorbent (MaA) was cogently synthesized in a hydrothermal reaction where a waste silica glass powder was mixed into NaOH solution. The satisfactory reaction properties were achieved by regulating the conditioning time (Ct), reaction temperature (Rt), and relative ratio of the reactants (Rr= SiO2:Na2O). XRF, XRD, SEM, BET, FTIR, AFM, TG and TEM analysis formed part of the selected samples. The prepared MaA adsorbent was then applied to treat Pb2+, Cd2+ and Cu2+ ions, thus effectively allowing the physicochemical properties (pH, temperature and contact duration), on the adsorption amount to be examined. Upon completion, the results indicated that the initial pH as well as the contact duration had notable effect on the adsorption amount. Conversely, the temperature change had an insignificant effect on the equilibrium adsorption amount. In addition, a dosage of 0.1 g of MaA, concentration of 1000 mg/L, pH ranging from 6−8, and temperature of about 25°C were found to be the optimum process conditions for the adsorption of the examined heavy metals, whereas difference in contact time was recorded as follows: 1 h for Pb2+ and Cu2+ ions with adsorption amounts of 75.081 mg/g and 74.054 mg/g, respectively; and 3 h for Cd2+ ion with adsorption equal to 75.530 mg/g. In the analysis of the trend, the coefficients of correlation (R2=0.99) of the Langmuir isotherm model were increasingly consistent compared to Freundlich isotherm model (R2 from 0.10 to 0.55), thus indicating that the process to be a homogeneous monomolecular layer adsorption. Moreover, the kinetic aspects were similarly consistent in relation to quasi-secondary kinetic equation, which then further established that the process was primarily controlled by ion exchange, extra-particle, intra-particle, and liquid film diffusion. In addition, research on the potential reusability of MaA adsorbent after being employed to treat heavy metals was also performed. The crystalline phase of the composite after subjected to high temperature indicated wollastonite (CaSiO₃) and gregoryite (Na₂CO₃) as the main mineralogical phases. These minerals are beneficial in the preparation of functional building materials by promoting a sustainable solution for the full recycling of waste glass and contributing to efficient solid waste management and environment protection.

Novel algae-chitosan/alginate beads for efficient basic Fuchsin removal: Synthesis, characterization, adsorption study, mechanism, and optimization

In this study, utilized algae activated with citric acid and lime juice to develop a novel bioadsorbent, The Algae@CS/Alginate beads were formed by encapsulating the activated algae with chitosan and alginate, producing a nanocomposite that is efficient in removing Basic Fuchsin (BF) dye from water. The beads were characterized by means of a diversity of techniques, such as FTIR, XRD, XPS, SEM and determination the surface area via N2 adsorption/desorption isotherm that permitted that the adsorbent has high surface area 124.43 m2/g. The electrical properties of the BF, including its structure and reactivity, were determined by density functional theory (DFT). The MEP data and the molecular orbitals (HOMO and LUMO), as well as the sites of the electrophilic besides nucleophilic attack places, correspond fairly well, according to DFT. The adsorption process was fitted to Langmuir isothermally, and kinetically to pseudo-second-order (PSOE) model. The adsorption mechanism was identified as chemisorption with an adsorption energy of 32.6 kJ/mol. Thermodynamic research shows that the BF adsorption process by Algae@CS/Alginate beads is spontaneous and endothermic because of the positive ΔHo and negative ΔGo. Through numerical optimization of the programmed, the ideal conditions for adsorption were strongminded to be a pH of 8, a dosage of 0.02 g/25 mL for Algae@CS/Alginate beads, and a concentration of 367.27 mg/g of BF. Using the least amount of intended experiments, the adsorption procedure was optimized by the request of Box-Behnken design (BBD) and answer surface methodology (RSM) in Design-Expert software. Adsorbent reusability test results showed that, following eight successive cycles of adsorption and desorption, the adsorbent was stable and that removal efficacy had not decreased. It additionally demonstrated good efficacy, no alteration in chemical conformation, and the same XRD and FTIR data before and after recycle. Analyze the interaction between the Algae@CS/Alginate beads and the BF.

Preparation of imprinted cryogels of cellulose cross-linked ionic liquids for selective separation of Gd(III) from rare earth leachate

The development of high technology has elevated industry’s dependence on rare earth resources. The hydrometallurgical process is widely used for the separation of rare earth elements (REEs) from rare earth ores, producing acidic leachate with trace amounts of REEs. Recovery of REEs from rare earth leachate not only mitigates the negative impact of leachate on the environment, but also contributes to the realization of sustainable resource utilization. In this study, two novel imprinted cryogel adsorbents, methyltrioctylammonium chloride-derivative carboxymethylated cellulose nanocrystal imprinted cryogel (LR-ICMC) and ethylmethylimidazolium bromide-derivative carboxymethylated cellulose nanocrystal imprinted cryogel (LM-ICMC), were constructed by using carboxymethylated modified cellulose nanocrystals as a backbone structure, and successfully branched ionic liquids (ILs) methyltrioctylammonium chloride-derivative and ethylmethylimidazolium bromide-derivative, respectively, for the separation of gadolinium ions (Gd(III)) from rare earth leachate. Firstly, SEM and TEM results showed that the incorporation of ILs retained part of the pore structure of carboxymethylated cellulose nanocrystals (CMCNCs). BET and TG results illustrated that the incorporation of ILs effectively increased the specific surface area and thermal stability of LR-ICMC and LM-ICMC. FT-IR and XPS results showed that LR-ICMC and LM-ICMC could adsorb Gd(III) by electrostatic and chelating effects. Secondly, adsorption isotherm experiments demonstrated the adsorption capacities of 66.880 mg/g and 75.895 mg/g for LR-ICMC and LM-ICMC, respectively; adsorption kinetic experiments demonstrated the ability of LR-ICMC and LM-ICMC to rapidly adsorb 85.152 % and 87.989 % of the maximum adsorption capacity, respectively, within the initial first 40 min. Finally, cycling experiments demonstrated the advantages of LR-ICMC and LM-ICMC in reuse, maintaining 89.245 % and 90.734 % of the original performance after five adsorption–desorption cycles, respectively. Based on these results, LR-ICMC and LM-ICMC were demonstrated to be highly efficient and reusable adsorbents for selective recovery of Gd(III) from rare earth leachate. This study deepens the application of ILs in solid-phase adsorbents and highlights the great potential of LR-ICMC and LM-ICMC in the field of REEs recovery.

Mercury Ion Selective Adsorption from Aqueous Solution Using Amino-Functionalized Magnetic Fe2O3/SiO2 Nanocomposite.

This study focuses on the development of new amino-functionalized magnetic Fe2O3/SiO2 nanocomposites with varying silicate shell ratios (1:0.5, 1:1, and 1:2) for the efficient elimination of Hg2+ ions found in solutions. The Fe2O3/SiO2-NH2 adsorbents were characterized for their structural, surface, and magnetic properties using various techniques, including Fourier transform infrared spectrum (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Braunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), zeta-potential, and particle size measurement. We investigated the adsorption circumstances, such as pH, dosage of the adsorbent, and duration of adsorption. The pH value that yielded the best results was determined to be 5.0. The Fe2O3/SiO2-NH2 adsorbent with a silicate ratio of (1:2) exhibited the largest amount of adsorption capacity of 152.03 mg g-1. This can be attributed to its significantly large specific surface area of 100.1 m2 g-1, which surpasses that of other adsorbents. The adsorbent with amino functionalization demonstrated a strong affinity for Hg2+ ions due to the chemical interactions between the metal ions and the amino groups on the surface. The analysis of adsorption kinetics demonstrated that the adsorption outcomes adhere to the pseudo-second-order kinetic model. The study of adsorption isotherms revealed that the adsorption followed the Langmuir model, indicating that the adsorption of Hg2+ ions with the adsorbent occurred as a monomolecular layer adsorption process. Furthermore, the thermodynamic analyses revealed that the adsorption of Hg2+ ions using the adsorbent was characterized by a spontaneous and endothermic process. Additionally, the adsorbent has the ability to selectively extract mercury ions from a complex mixture of ions. The Fe2O3/SiO2-NH2 nanocomposite, which is loaded with metal, can be easily recovered from a water solution due to its magnetic properties. Moreover, it can be regenerated effortlessly through acid treatment. This study highlights the potential use of amino-functionalized Fe2O3/SiO2 magnetic nanoparticles as a highly efficient, reusable adsorbent for the removal of mercury ions from contaminated wastewater.

Porous sodium alginate/cellulose nanofiber composite hydrogel microspheres for heavy metal removal in wastewater

High adsorption capacity, high adsorption rate and reusable adsorbents are urgent needed for removing heavy metals from wastewater. In this study, porous sodium alginate/cellulose nanofiber (SA/CNF) composite hydrogel microspheres were prepared by combining sodium alginate with cellulose nanofibers by microfluidics technology and adding polyethylene glycol (PEG) as pore making agent. The SA/CNF composite hydrogel microspheres could efficiently adsorb heavy metals (Pb2+, Cu2+ and Cd2+) in wastewater. The influencing factors of adsorption process, including pH, temperature, initial concentration, coexisting ions and aquatic environments, were systematically discussed. The adsorption process was more consistent with Langmuir isotherm model and pseudo-second-order model in batch system, indicating the adsorption process was mainly chemical adsorption. The adsorption capacity to Pb2+ obtained by Langmuir model was as high as 544.66 mg/g at 20 °C. Fixed-bed column adsorption experiments demonstrated the excellent performance of the as-prepared SA/CNF microspheres for treatment of the flowing wastewater in a column system. Overall, a highly practical adsorption process based on hydrogel adsorbents was developed for the removal of heavy metals from actual wastewater.

FACILE SYNTHESIS OF ACTIVATED CARBON/ALGINATE/CHITOSAN COMPOSITE BEADS AS RHEMAZOLE BRILLIANT BLUE R ADSORBENT

Developing composite beads composed of chitosan, alginate, and activated carbon for dye removal is essential due to their improved adsorption capabilities and environmental benefits. By utilizing natural resources efficiently for an effective dye removal process, this study developed an activated carbon/alginate/chitosan composite bead as Rhemazole Brilliant Blue R (RBBR) adsorbent. The surface shape of composites exhibits more protrusions, grooves, and asymmetric pores than activated carbon, which could improve dye adsorption capability. FTIR analysis verified that functional groups such as OH, NH, protonated amine, and carboxylate from the constituent polymers were enriched in the activated carbon/alginate/chitosan composite. These groups also function as active sites for adsorbents. It was aligned with the composite beads' Freundlich isotherm model, which shows that heterogeneous or many active sites contribute to adsorption and provide multilayer adsorption. The kinetic model of pseudo-second order fits well with the adsorption process, indicating that chemisorption is the rate-limiting step in RBBR adsorption. The optimum adsorption conditions were at pH 1, with an adsorbent dose of 0.08 g, RBBR dye concentration of 125 mg/L, and a contact time of 60 min. The composite beads also exhibit stability in acidic and basic solutions, with the effectiveness of being reused up to four times, providing a reusable adsorbent with versatility in various water treatment conditions. Hence, synthesizing activated carbon/alginate/chitosan composite beads presents a promising solution for sustainable wastewater treatment based on biodegradable and eco-friendly composite.

Effective Removal of Cu(II) Ions from Aqueous Solution by Cross-Linked Chitosan-Based Hydrogels

The elimination of metal ions from industrial waste water is one of the most significant environmental needs. For the first time, two chitosan hydrogels that we had previously synthesized, cross-linked with varying concentrations of trimellitic anhydride isothiocyanate (represented by H1 and H2), were utilized in this investigation to adsorb Cu(II) ions. We found that pH 6, 25 °C, 200 mg L−1 of Cu(II) ions concentration, and 15 mg of hydrogel dosage were the ideal parameters for Cu(II) ion elimination. The kinetics of their adsorption fitted to the pseudo-second-order model with the highest correlation coefficient (R2) values equal to 0.999 and 1.00 for H1 and H2, respectively. The experimental qe values were found when H1 was equal to 97.59 mg g−1 (theoretical value is equal to 98.04 mg g−1) and H2 was equal to 96.20 mg g−1 (theoretical value is equal 99.01 mg g−1). The hydrogels achieved a removal effectiveness of 97.59% and their adsorption isotherms matched the Freundlich model, indicating the multi-layered and homogeneous adsorption nature. The removal of copper ions is significantly driven by the physisorption phenomenon. The hydrogels have a great possibility to be utilized as promising, efficacious, reusable adsorbents for industrial wastewater remediation. Thus, incorporation of a cross-linker, containing binding centers for Cu(II) ions, between chitosan chains is a good way to obtain suitable efficient adsorbents which are good choices for application in the field of metal elimination.

Sustainable remediation of a cationic dye in aqueous solutions using modified palm petiole as a highly efficient and reusable adsorbent

Sustainable remediation of a cationic dye in aqueous solutions using modified palm petiole as a highly efficient and reusable adsorbent

Utilization of dragon fruit (Hylocereus undatus) peel-derived biochar for the adsorptive removal of tetracycline from aqueous solution

The peel of Hylocereus undatus was employed in the preparation of biochar and firstly applied for tetracycline removal from aqueous solution. Based on different characterization techniques, the material was found to possess a variety of surface functional groups on a porous structure and a pH point of zero charge (pHpzc) of 9.3. Adsorption of tetracycline (TC) was conducted under varying conditions, revealing significant effects of carbonization temperature, solution pH, adsorbent dose, ionic strength, contact time and initial concentration of TC on the biochar adsorption capacity. Kinetic data on TC adsorption were best described using the Elovich kinetic model, with an initial adsorption rate of 167.3 mg g−1 min−1. Isotherm data on adsorption of the desired biochar showed the best fit with the Temkin isotherm model, followed by the Langmuir model, displaying maximum adsorption capacity at 12.4 mg g−1. The electrostatic interactions between the charged biochar surfaces and certain fractions of TC were proposed as the major mechanism, together with H-bonding, pore-filling effect and π–π interaction. This study demonstrates great potential of H. undatus peel as a starting material to prepare an effective and reusable adsorbent in the removal of TC.

Prospective application of eco-friendly banana peel reduced graphene oxide (BRGO) for aqueous Cr (VI) and acid dye adsorption: A waste utilization approach

Banana peels are an environmentally benign alternative to toxic reducing agents. Banana peel-reduced graphene oxide (BRGO) showed high performance in the adsorption of metal and dye ions. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and a Zeta potential analyzer were used to characterize the BRGO. Different influencing factors such as pH, dose, concentration, duration, and temperature, were studied to evaluate the efficiency of the adsorbent. The Langmuir and Freundlich isotherm models were fitted for Cr (VI) and acid dye adsorption. The maximum adsorption capacity (qm) of BRGO for Cr (VI) and AV54 dye were 135.87 and 110.74 mg/g, respectively. The pseudo-second-order kinetic model was better suited for Cr (VI) and AV54 dye adsorption, which indicated chemical adsorption. Thermodynamically, the adsorption exhibited spontaneity and was endothermic. Regeneration and reuse of adsorbents were also studied for potential use in treating tannery effluent.

Facile green fabrication of MIL‐101(Cr)/PVA nanofiber composite as effective, stable, and reusable adsorbent for cationic dye removal

AbstractIn this study, chromium‐based metal–organic framework (MIL‐101(Cr)) was incorporated into polyvinyl alcohol nanofibers (PVA NFs) via green electrospinning followed by heat treatment to fabricate MIL‐101(Cr)@PVA NFs composite without the need for any organic solvent or other dispersants. The fabricated MIL‐101(Cr)@PVA NFs were comprehensively characterized using a suite of common techniques. Morphological characteristics of MIL‐101(Cr)@PVA NFs showed a fibrous structure with an average diameter of 228 ± 37 nm and decorated with MIL‐101(Cr) particles arranged in a nanoneedle‐like pattern. Subsequently, its adsorption efficiency towards the cationic crystal violet dye (CV) was evaluated through batch adsorption experiments. The influence of various experimental parameters on CV removal efficiency was systematically optimized using a factorial design approach. The Langmuir isotherm and kinetic pseudo‐second‐order (PSO) model provided an excellent fit to the adsorption equilibrium data, indicating a maximum adsorption capacity (qmax) of 344.18 mg/g for MIL‐101(Cr)@PVA NFs compared with 83.94 mg/g for pristine PVA NFs. Furthermore, the MIL‐101(Cr)@PVA NFs composite demonstrated excellent reusability and stability, maintaining a significant portion of its removal capacity even after six adsorption–desorption cycles. These findings highlight the potential of the fabricated composite as a highly efficient and reusable adsorbent for CV removal from wastewater treatment applications.Highlights The MIL‐101(Cr)@PVA NFs nanocomposite fabricated by electrospinning technique. The MIL‐101(Cr) particle arranged in a nanoneedle‐like pattern in the PVA NFs. Incorporation of MIL‐101(Cr) improved qmax of PVA by 391.5%. The MIL‐101(Cr)@PVA NFs membrane has excellent stability and reusability.