Isotherm, Thermodynamics, and Kinetics of Methyl Orange Adsorption onto Magnetic Resin of Chitosan Microspheres

Preparation of chitosan resin by two-step crosslinking method and its adsorption for palladium in wastewater

To preserve the activity of amine groups on chitosan, chitosan resin (CR) was synthesized using the reversed-phase suspension two-step crosslinking method for the adsorption of palladium from wastewater. The effects of varying the amounts of chitosan, liquid paraffin, ethyl acetate, formaldehyde solution, and epichlorohydrin on the adsorption capacity of CR were investigated using both single-factor experiments and response surface methodology. The preparation conditions for the chitosan resin were optimized, and its adsorption properties were systematically evaluated. The results indicated that CR exhibited a high saturated adsorption capacity for palladium, reaching 195.22 mg·g-1. The adsorption kinetics followed the pseudo-second-order model, while the adsorption isotherms were well described by the Sips model. Thermodynamic analysis demonstrated that the adsorption process was spontaneous and endothermic. Furthermore, CR maintained exceptional stability, with a palladium removal efficiency exceeding 99.8 % even after eight adsorption-desorption cycles. The primary adsorption mechanism is attributed to the interaction between palladium ions and the protonated amino groups of the chitosan resin.

Investigation of MO Adsorption Kinetics and Photocatalytic Degradation Utilizing Hollow Fibers of Cu-CuO/TiO2 Nanocomposite

This comprehensive study explores the kinetics of adsorption and its photocatalytic degradation of methyl orange (MO) using an advanced copper-decorated photocatalyst in the form of hollow fibers (HFs). Designed to boost both adsorption capacity and photocatalytic activity, the photocatalyst was tested in batch experiments to efficiently remove MO from aqueous solutions. Various isotherm models, including Langmuir, Freundlich, Sips, Temkin, and Dubinin-Radushkevich, along with kinetic models like pseudo-first and pseudo-second order, Elovich, Bangham, and Weber-Morris, were utilized to assess adsorption capacity and kinetics at varying initial concentrations. The results indicated a favorable MO physisorption on the nanocomposite photocatalyst under specific conditions. Further analysis of photocatalytic degradation under UV exposure revealed that the material maintained high degradation efficiency and stability across different MO concentrations. Through the facilitation of reactive oxygen species generation, oxygen played a crucial role in enhancing photocatalytic performance, while the degradation process following the Langmuir-Hinshelwood model. The study also confirmed the robustness and sustained activity of the nanocomposite photocatalyst, which could be regenerated and reused over five successive cycles, maintaining 92% of their initial performance at concentrations up to 15 mg/L. Overall, this effective nanocomposite photocatalyst structured in the form of HF shows great promise for effectively removing organic pollutants through combined adsorption and photocatalysis, offering valuable potential in wastewater treatment and environmental remediation.

Exploring the potent hydrolytic activity of chitosan-cerium complex microspheres resin for organophosphorus pesticide degradation

Chitosan is a biocompatible, non-toxic and renewable natural basic polysaccharide that can be cross-linked and reacted with Ce(IV) to form a physiologically active chitosan-Ce(IV) complex. To investigate this novel complex and its potential to hydrolyze phosphate ester bonds, chitosan-cerium complex microspheres resin (CS-CCMR) was prepared from chitosan and ceric ammonium nitrate by reversed-phase suspension cross-linking polymerization. CS-CCMR was characterized, its ability to hydrolyze disodium p-nitrobenzene phosphate (PNPP2Na) and organophosphorus pesticides was investigated, and the hydrolytic mechanism was explored. CS-CCMR was composed of dark yellow microspheres with smooth surfaces and dense pores. It was found that CS-CCMR contained 4.507 mg/g Ce(IV), indicating that coordination polymerization between Ce(IV) and chitosan was successful. The presence of Ce(IV) in CS-CCMR was confirmed by multiple analytical methods and it was found that coordination of Ce(IV) by chitosan was mediated by the nitrogen atom of the amino group and the oxygen atom of the hydroxyl group of chitosan. It was shown that CS-CCMR efficiently hydrolyzed the phosphate ester bonds of PNPP2Na and five organophosphorus pesticides. Hydrolysis of PNPP2Na is potentially accomplished by charge neutralization and nucleophilic substitution. The mechanism of parathion degradation by CS-CCMR involves modification of the nitro group to give aminoparathion, followed by cleavage of the P-O bond to generate diazinphos. Consequently, the novel chitosan-Ce(IV) complex exhibits great efficiency for hydrolysis of phosphate ester bonds and CS-CCMR is expected to be developed as an agent to reduce the possibility of contamination of fruit and vegetable drinks by organophosphorus pesticides.

Chitosan: Structural and Chemical Modification, Properties, and Application

Chitosan is a polymer of natural origins that possesses many favourable properties [...].

Abalone shell-based magnetic macroporous hydroxyapatite microspheres with good reusability for efficient dye adsorption

Azo dye methyl orange (MO) and shell rotting cause great environmental pollution. Most of the common dye adsorbents are difficult to produce, not environmentally friendly and it is always difficult to utilize the shell resources effectively. In this study, shell-based economical and environmentally friendly magnetic hydroxyapatite microsphere adsorbents (Fe3O4 @SiO2/HAP) were developed for the removal of MO from simulated wastewater by sol-gel and hydrothermal synthesis methods. The effects of solution pH, initial concentration, adsorption time and system temperature on the adsorption effect were investigated, and the repeat recovery performance was explored. The equilibrium adsorption data follow the Freundlich isotherm and pseudo-second-order kinetic curves, and the analysis indicates that the adsorption process is spontaneously exothermic. The adsorption capacities of MO were up to 94.48% and 88.94%, under the acidic environment of pH = 4, respectively, and had good recycling performance. The results provide a high-value utilization pathway for waste shell resources and focus on the removal of azo dyes. This is expected to provide new development ideas for the environmental hazards caused by acid dye wastewater discharged into rivers and oceans, as well as the problems of soil pollution and resource waste caused by weathering and corrosion of shells.

Adsorption of ibuprofen using waste coffee derived carbon architecture: Experimental, kinetic modeling, statistical and bio-inspired optimization

Pharmaceuticals in water are a growing environmental concern, as they can harm aquatic life and human health. To address this issue, an adsorbent made from coffee waste that effectively removes ibuprofen (a common pharmaceutical pollutant) from wastewater was developed. The experimental adsorption phase was planned using a Design of Experiments approach with Box-Behnken strategy. The relation between the ibuprofen removal efficiency and various independent variables, including adsorbent weight (0.01-0.1 g) and pH (3-9), was evaluated via a regression model with 3-level and 4-factors using the Response surface methodology (RSM) . The optimal ibuprofen removal was achieved after 15 min using 0.1 g adsorbent at 32.4 °C and pH = 6.9. Moreover, the process was optimized using two powerful bio-inspired metaheuristics (Bacterial Foraging Optimization and Virus Optimization Algorithm). The adsorption kinetics, equilibrium, and thermodynamics of ibuprofen onto waste coffee-derived activated carbon were modeled at the identified optimal conditions. The Langmuir and Freundlich adsorption isotherms were implemented to investigate adsorption equilibrium, and thermodynamic parameters were also calculated. According to the Langmuir isotherm model, the adsorbent's maximum adsorption capacity was 350.00 mg g-1 at 35 °C. The findings revealed that the ibuprofen adsorption was well-matched with the Freundlich isotherm model, indicating multilayer adsorption on heterogeneous sites. The computed positive enthalpy value showed the endothermic nature of ibuprofen adsorption at the adsorbate interface.

Effective Adsorptive Removal of Coomassie Violet Dye from Aqueous Solutions Using Green Synthesized Zinc Hydroxide Nanoparticles Prepared from Calotropis gigantea Leaf Extract

The removal of color from dye wastewater is crucial, since dyes are extremely toxic and can cause cancer in a variety of life forms. Studies must be done to use cost-effective adsorbents for the removal of color from dye effluents to protect the environment. To our knowledge, virtually no research has been done to describe the possibility of using Calotropis gigantea leaf extract zinc hydroxide nanoparticles (CG-Zn(OH)2NPs) as an adsorbent for the decolorization of Coomassie violet (CV) from the aqueous emulsion, either in batch mode or continuously. In the present batch investigation, CV dye is removed from the synthetic aqueous phase using CG-Zn(OH)2NPs as an adsorbent. The synthesized nanoparticles were characterized using various instrumental techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller (BET) surface area and pore volume, a particle size analyser, and zero-point charge. The decolorization efficacy of CV dye from an aqueous phase by the adsorbent was examined in batch mode by varying process parameters. The consequences of various experimental variables were optimized using response surface methodology (RSM) to achieve the maximum decolorization efficiency (90.74%) and equilibrium dye uptake, qe (35.12 mg g−1). The optimum pH, dye concentration, CG-Zn(OH)2NPs adsorbent dosage, and particle size were found to be 1.8, 225 mg L−1, 5 g L−1, and 78 μm, respectively for CV dye adsorption capacity at equilibrium. The adsorbent zero-point charge was found to be at pH 8.5. The Langmuir isotherm model provided a good representation of the equilibrium data in aqueous solutions, with a maximum monolayer adsorption capability (qmax) of 40.25 mg g−1 at 299 K. The dye adsorption rate follows a pseudo-second-order kinetic model at various dye concentrations, which indicated that the reaction is more chemisorption than physisorption. The negative values of ΔG and positive values of ΔH at different temperatures indicate that the adsorption process is spontaneous and endothermic, respectively. Reusability tests revealed that the prepared nanoparticles may be used for up to three runs, indicating that the novel CG-Zn(OH)2NPs seems to be a very promising adsorbent for the removal of Coomassie violet dye from wastewater.