Porous magnetic resin-g-chitosan beads for adsorptive removal of phenolic compounds

Biopolymer-based beads for the adsorptive removal of organic pollutants from wastewater: Current state and future perspectives

Among biopolymer-based adsorbents, composites in the form of beads have shown promising results in terms of high adsorption capacity and ease of separation from the effluents. This review addresses the potential of biopolymer-based beads to remediate wastewaters polluted with emerging organic contaminants, for instance dyes, active pharmaceutical ingredients, pesticides, phenols, oils, polyaromatic hydrocarbons, and polychlorinated biphenyls. High adsorption capacities up to 2541.76 mg g-1 for dyes, 392 mg g-1 for pesticides and phenols, 1890.3 mg g-1 for pharmaceuticals, and 537 g g-1 for oils and organic solvents have been reported. The review also attempted to convey to its readers the significance of wastewater treatment through adsorption by providing an overview on decontamination technologies of organic water contaminants. Various preparation methods of biopolymer-based gel beads and adsorption mechanisms involved in the process of decontamination have been summarized and analyzed. Therefore, we believe there is an urge to discuss the current state of the application of biopolymer-based gel beads for the adsorption of organic pollutants from wastewater and future perspectives in this regard since it is imperative to treat wastewater before releasing into freshwater bodies.

Oil palm frond-derived cellulose nanocrystals: Effect of pretreatment and elucidating its reinforcing potential in hydrogel beads

Herein, cellulose nanocrystals were synthesized from oil palm fronds (CNC-OPF) involving two pretreatment approaches, viz. autohydrolysis and soda pulping. The pretreatments were applied individually to OPF fibers to assess their influence on CNCs' physicochemical and thermal properties. CNC-OPF samples were assessed using complementary characterization techniques, which confirmed their purity and characteristics. CP/MAS 13C NMR and TEM studies revealed that autohydrolysis pretreatment yielded CNCs with effective hemicellulose and extractives removal compared to that of soda pulping. XRD analysis demonstrated that autohydrolysis-treated CNC-OPF contained a much higher crystallinity index compared to soda pulping treatment. BET measurement disclosed a relatively higher surface area and wider pore diameter of autohydrolysis-treated CNC-OPF. Autohydrolysis-treated CNCs were applied as a reinforcement filler in alginate-based hydrogel beads for the removal of 4-chlorophenol from water, which attained a qmax of 19.168 mg g-1. BET analysis revealed the less porous nature of CNC-ALG hydrogel beads which could have contributed to hydrogel beads' relatively lower adsorption capacity. The point of zero charge of CNC-ALG hydrogel beads was 4.82, suggesting their applicability only within a short solution pH range. This study directs future studies to unveil the possibilities of functionalizing CNCs in order to enhance the adsorption performance of CNC-immobilized hydrogel beads towards 4-chlorophenol and other organic contaminants.

The use of chitosan-based composites for environmental remediation: A review

The presence of hazardous pollutants in water sources as a result of industrial activities is a major environmental challenge that impedes the availability of safe drinking water. Adsorptive and photocatalytic degradative removal of various pollutants in wastewater have been recognized as cost-effective and energy-efficient strategies. In addition to its biological activity, chitosan and its derivatives are considered as promising materials for the removal of various pollutants. The abundance of hydroxyl and amino groups in the chitosan macromolecular structure results in a variety of concurrent pollutant's adsorption mechanisms. Furthermore, adding chitosan to photocatalysts increases the mass transfer while decreasing both the band gap energy and the amount of intermediates produced during photocatalytic processes, improving the overall photocatalytic efficiency. Herein, we have reviewed the current design and preparation of chitosan and its composites, as well as their applications for the removal of various pollutants by adsorption and photocatalysis processes. Effects of operating variables such as the pH, catalyst mass, contact time, light wavelength, initial pollutant's concentration, and catalyst recyclability, are discussed. Various kinetic and isotherm models are presented to elucidate the rates, and mechanisms of pollutant's removal, onto chitosan-based composites, and several case studies are presented. Additionally, the antibacterial activity of chitosan-based composites has been discussed. This review aims to provide a comprehensive and up-to-date overview of the applications of chitosan-based composites in wastewater treatment and put forward new insights for the development of highly effective chitosan-based adsorbents and photocatalysts. Finally, the main challenges and future directions in the field are discussed.

Efficient phenolic compounds adsorption by immobilization of copper-based metal-organic framework anchored polyacrylonitrile/chitosan beads

The application of newly formulated beads from copper-benzenetricarboxylate (Cu-BTC), polyacrylonitrile (PAN), and chitosan (C), Cu-BTC@C-PAN, C-PAN, and PAN, for the removal of phenolic chemicals from water, is described in the current paper. Phenolic compounds (4-chlorophenol (4-CP) and 4-nitrophenol (4-NP)) were adsorbed using beads and the adsorption optimization looked at the effects of several experimental factors. The Langmuir and Freundlich models were used to explain the adsorption isotherms in the system. A pseudo-first and second-order equation is performed for describing the kinetics of adsorption. The obtained data fit (R² = 0.999) supports the suitability of the Langmuir model and pseudo-second-order kinetic equation for the adsorption mechanism. Cu-BTC@C-PAN, C-PAN, and PAN beads' morphology and structure were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transforms infrared spectroscopy (FT-IR). According to the findings, Cu-BTC@C-PAN has very high adsorption capacities of 277.02, and 324.74 mg g^-1, for 4-CP and 4-NP, respectively. The Cu-BTC@C-PAN beads showed 2.55 times higher adsorption capacity than PAN in the case of 4-NP, but in the case of 4-CP, it was higher by 2.64 times.

Arsenic in drinking water: overview of removal strategies and role of chitosan biosorbent for its remediation

Accessibility to clean drinking water often remains a crucial task at times. Among other water pollutants, arsenic is considered a more lethal contaminant and has become a serious threat to human life globally. This review discussed the sources, chemistry, distribution, and toxicity of arsenic and various conventional technologies that are in option for its removal from the water system. Nowadays, biosorbents are considered the best option for arsenic-contaminated water treatment. We have mainly focused on the need and potential of biosorbents especially the role of chitosan-based composites for arsenic removal. The chitosan-based sorbents are economically more efficient in terms of their, low toxicity, cost-effectiveness, biodegradability, eco-friendly nature, and reusability. The role of various modification techniques, such as physical and chemical, has also been evaluated to improve the physicochemical properties of biosorbent. The importance of adsorption kinetic and isotherm models and the role of solution pH and pH_PZC for arsenic uptake from the polluted water have also been investigated. Some other potential applications of chitosan-based biosorbents have also been discussed along with its sustainability aspect. Finally, some suggestions have been highlighted for further improvements in this field.

A review on the adsorption mechanism of different organic contaminants by covalent organic framework (COF) from the aquatic environment

Recently, covalent organic frameworks (COFs) have gained significant attention as a promising material for the elimination of various organic pollutants due to their distinctive characteristics such as high surface area, adjustable porosity, high removal efficiency, and recyclability. The efficiency and selectivity of COFs depend on the decorated functional group and the pore size of the chemical structure. Hence, this review highlights the adsorption removal mechanism of different organic contaminants such as (pharmaceutical and personal care products, pesticides, dyes, and industrial by-products) by COFs from an aqueous solution. Spectroscopic techniques and theoretical calculation methods are introduced to understand the mechanism of the adsorption process. Also, a comparison between the performance of COFs and other adsorbents was discussed. Furthermore, future research directions and challenges encountered in the removal of organic contaminants by COFs are discussed.

Boron Removal by Sorption on Modified Chitosan Hydrogel Beads

An excess concentration of boron in irrigation and drinking water can negatively affect the yield of plants and the human nervous system, respectively. To meet the recommended levels, hybrid biosorbent hydrogel beads based on chitosan and manganese (II-IV) were employed for the removal of boron from aqueous media. The results showed that the biosorbent effectively removed boric acid from the aqueous medium at neutral pH over a sorption time of 2 h and the liquid/hydrogel ratio of 20 mL/g, achieving a maximum sorption capacity near 190 mg/g. The modeling of the sorption equilibrium data indicated that the Freundlich isotherm equation gave the best fit out of the isotherm models examined. A pseudo-second-order model was found to best describe the sorption kinetics. The favorable attachment of manganese to the chitosan structure enabled the sorption of boron and was confirmed by FTIR, RS, XRD, SEM and ICP-OES methods. Boron desorption from the spent biosorbent was successfully achieved in three cycles using a NaOH solution. In general, the results of this research indicate that this method is one of the possibilities for improving water quality and may contribute to reducing pollution of the aquatic environment.

Efficiency of magnetic chitosan supported on graphene for removal of perchlorate ions from wastewater

In this study, we used a synthesized cross-linked magnetic chitosan with graphene oxide beads to study the removal of perchlorate from wastewater. The prepared complex was characterized using transmission electron microscopy (TEM), Fourier Transformation Infrared spectroscopy (FT-IR), vibrating sample magnetometry (VSM) and Thermal gravimetric analysis (TGA). Several parameters were studied including the effect of pH, contact time and the co-existing anions. The study showed that the adsorption could be studied in a wide range of pH. The study showed that the adsorption follows a pseudo-second-order model and Langmuir adsorption isotherm. The enthalpy and negative Gibbs standard free energy showed that the adsorption process was exothermic and spontaneous. The perchlorate adsorbent can be regenerated well by 0.1% NaCl solution.

An Overview and Evaluation of Highly Porous Adsorbent Materials for Polycyclic Aromatic Hydrocarbons and Phenols Removal from Wastewater

Polycyclic aromatic hydrocarbons (PAHs) and phenolic compounds had been widely recognized as priority organic pollutants in wastewater with toxic effects on both plants and animals. Thus, the remediation of these pollutants has been an active area of research in the field of environmental science and engineering. This review highlighted the advantage of adsorption technology in the removal of PAHs and phenols in wastewater. The literature presented on the applications of various porous carbon materials such as biochar, activated carbon (AC), carbon nanotubes (CNTs), and graphene as potential adsorbents for these pollutants has been critically reviewed and analyzed. Under similar conditions, the use of porous polymers such as Chitosan and molecularly imprinted polymers (MIPs) have been well presented. The high adsorption capacities of advanced porous materials such as mesoporous silica and metal-organic frameworks have been considered and evaluated. The preference of these materials, higher adsorption efficiencies, mechanism of adsorptions, and possible challenges have been discussed. Recommendations have been proposed for commercialization, pilot, and industrial-scale applications of the studied adsorbents towards persistent organic pollutants (POPs) removal from wastewater.

Removal of phenol from aqueous solution using acid-modified Pseudomonas putida-sepiolite/ZIF-8 bio-nanocomposites

The discharge of phenol, a harmful pollutant, in the environment poses a threat to human health. With the rapid urbanization and industrialization of the land, there is a pressing need to find new technologies and efficient adsorption materials to address phenol contamination. As a potential adsorbent candidate, sepiolite (SEP) has garnered much interest owing to its large specific surface area, and excellent adsorption performance and biocompatibility. Herein, nanocomposite CESEP/ZIF-8, consisting of zeolite imidazole framework (ZIF-8) and hydrochloric acid-modified SEP (CESEP), was prepared and examined toward the adsorption of phenol. Adsorption equilibrium was achieved within 150 min at initial phenol solution concentrations of 10 and 20 mg/L. However, complete removal was not achieved. Accordingly, biodegradation was introduced. Microorganism Pseudomonas putida was immobilized onto CESEP/ZIF-8, which afforded synergistic adsorption and biodegradation action. Phenol at solution concentrations of 10 and 20 mg/L was effectively removed within 13 and 24 h, respectively (as opposed to 21 and 36 h when phenol was removed in the presence of free Pseudomonas putida solely). The synergistic physical-biological treatment presented herein is expected to have great potential in the field of wastewater treatment.