Investigation of adsorption of organic dyes present in wastewater using chitosan beads immobilized with biofabricated CuO nanoparticles

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.

Sequential removal of phosphate and copper(II) ions using sustainable chitosan biosorbent

Although adsorbents are good candidates for removing phosphorus and heavy metals from wastewater, the use of biosorbents for the sequential treatment of phosphorus and copper has not yet been studied. Porous chitosan (CS)-based biosorbents (CGBs) were developed to adsorb phytic acid (PA), a major form of organic phosphate. This first adsorbate (PA) further served as an additional ligand (P-type ligand) for the CGBs (N-type ligand) to form a complex with the second adsorbate (copper). After the adsorption of PA (the first adsorbate), the spent CGBs were recycled and used as a new adsorbent to adsorb Cu(II) ions (the second adsorbate), which was expected to have a dual coordination effect through P, N-ligand complexation with copper. The interactions and complexation between CS, PA and Cu(II) ions on the PA-adsorbed CGBs (PACGBs) were investigated by performing FTIR, XPS, XRD, and SEM-EDS analyses. The PACGBs exhibited fast and enhanced adsorption of Cu(II) ions, owing to the synergistic effect of the amino groups of CS (the original ligand, N-type) and the phosphate groups of PA (an additional ligand, P-type) on the adsorption of Cu(II) ions. This is the first time that sequential removal of phosphorus and heavy metals by biosorbents has been performed using biosorbents.

Removal of textile pollutants from aqueous medium using biosynthesized CuO nanoparticles: Theoretical comparative investigation via analytical model

The work deals with the removal of two dyes, namely methylene blue (MB) and methyl orange (MO), from polluted water by adsorption onto CuO nanoparticles synthesized with a green synthesis procedure, starting from plant resources. Adsorption isotherms are determined at different temperatures aiming at investigating the adsorption mechanisms of the two dyes. The experimental results indicate that, for both MB and MO, the adsorption capacity increases with increasing temperature, with slight differences in the case of MO. Comparatively, the CuO nanoparticles show a higher MB adsorption capacity with respect to MO. A modelling analysis is carried out with a multilayer model derived from statistical physics, selected among a group of models, each hypothesizing a different number of adsorbed molecules layers. The analysis of model parameters allows determining that the adsorbate molecules exhibit a non-parallel orientation on the surface of biosynthesized CuO nanoparticles and each functional group of the adsorbent binds multiple molecules, simultaneously.The model also allows determining the number of dye molecule layers formed on adsorbent surface, in all the cases resulting higher than three, also confirming the effect of temperature on the maximum adsorption capacity.Specifically, the total number of dye layers formed on biosynthesized CuO nanoparticles surface exhibited a range of 4.17-4.55 for MB dye and of 3.01-3.51 for MO dye.Finally, the adsorption energies reveal that adsorption likely involves physical forces (all resulting all below 22 kJ/mol), i.e. hydrogen bonding and van der Waals forces. The adsorption energies for the interactions between dye molecules are lower than those calculated for the interactions between the dye molecules and the adsorbent surface.

Design of chitosan/boehmite biocomposite for the removal of anionic and nonionic dyes from aqueous solutions: Adsorption isotherms, kinetics, and thermodynamics studies

This study introduces a chitosan/boehmite biocomposite as an efficient adsorbent for removing anionic Congo Red (CR) and non-ionic Bromothymol Blue (BTB) from water. Boehmite nanoparticles were synthesized using the Sol-gel method and then attached to chitosan particles using sodium tripolyphosphate through co-precipitation method. Characterized through FTIR, FE-SEM, BET, and XRD, the biosorbent displayed structural integrity with optimized pH conditions of 3 for CR and 4 for BTB, achieving over 90 % adsorption within 30 min. Pseudo second order kinetics model and Langmuir isotherm revealed monolayer sorption with capacities of 64.93 mg/g for CR and 90.90 mg/g for BTB. Thermodynamics indicated a spontaneous and exothermic process, with physisorption as the primary mechanism. The biosorbent demonstrated excellent performance and recyclability over five cycles, highlighting its potential for eco-friendly dye removal in contaminated waters.

Functionalizing natural polymers to develop green adsorbents for wastewater treatment applications

The present study provides an overview of scientific developments made in the last decade in the field of green adsorbents focusing on the modifications in natural polymers and their applications such as, wastewater treatment, and ion exchange. For this purpose, an introduction to the various methods of modifying natural polymers is first given, and then the properties, application, and future priorities of green adsorbents are also discussed. Methods of modification of natural polymers under homogeneous and heterogeneous conditions using modifiers with different properties are also described. Various methods for modifying natural polymers and the use of the obtained green adsorbents are reviewed. A comparison of the sorption properties of green adsorbents based on natural polymers and other adsorbents used in industry has also been carried out. With the participation of green adsorbents based on natural polymers, the properties of treated wastewaters having toxic metal ions, organic dyes, petroleum products, and other harmful compounds was analyzed. Future perspectives on green adsorbents based on natural polymers are as also highlighted.

Development of a chitosan/nanosilica biocomposite with arene functionalization via hydrothermal synthesis for acid red 88 dye removal

Herein, the polymer nanomatrix of chitosan/SiO2 (CHI/n-SiO2) was enriched with a π-π electron donor-acceptor system using diaromatic rings of benzil (BEZ) assisted via a hydrothermal process to obtain an effective adsorbent of chitosan-benzil/SiO2 (CHI-BEZ/n-SiO2). The polymer nanomatrix (CHI/n-SiO2) and the resulting adsorbent (CHI-BEZ/n-SiO2) were applied to remove the anionic acid red 88 (AR88) dye from aqueous media in a comparative mode. Box-Behnken design (BBD) was adopted to optimize AR88 adsorption onto CHI/n-SiO2 and CHI-BEZ/n-SiO2 with respect to variables that influence AR88 adsorption (adsorbent dose: 0.02-0.1 g/100 mL; pH: 4-10; and time: 10-90). The adsorption studies at equilibrium were conducted with a variety of initial AR88 dye concentrations (20-200 mg/L). The adsorption isotherm results reveal that the AR88 adsorption by CHI/n-SiO2 and CHI-BEZ/n-SiO2 are described by the Langmuir model. The kinetic adsorption profiles of AR88 with CHI/n-SiO2 and CHI-BEZ/n-SiO2 reveal that the pseudo-first-order model provides the best fit results. Interestingly, CHI-BEZ/n-SiO2 has a high adsorption capacity (261.2 mg/g), which exceeds the adsorption capacity of CHI/n-SiO2 (215.1 mg/g) that relates to the surface effects of SiO2 and the functionalization of chitosan with BEZ. These findings show that CHI-BEZ/n-SiO2 represents a highly efficient adsorbent for the removal of harmful pollutants from water, which outperforming the CHI/n-SiO2 system.

Biosynthesis of green CuO@C nanocomposite using Combretum indicum flower extract for organic dye removal: adsorption performance, modeling, and recyclability studies

Water contamination becomes one of the most high-priority environmental concerns, calling for the efficient treatment techniques. Bionanocomposites can be robust adsorbents, but the synthesis requires toxic chemicals or energy consuming and cause the secondary pollution. Green nanocomposites can be biogenically synthesized using the plant extract to end up with a critically safe strategy. Herein, we used the flower extract of Combretum indicum plant as a bio-based reductant and carbonaceous source for the green CuO@C nanocomposite. This green nanoadsorbent obtained a specific surface area of 17.33 m2/g, good crystallinity, and functional group-containing surface, i.e., -OH and -CONH-. We also conducted the optimization of parameters, i.e., concentration, CuO@C dose, pH, time, and temperature, and reached removal efficiencies towards malachite green (MG, 83.23%), Congo red (CR, 84.60%), brilliant blue (BB, 71.39%), and methylene blue (MB, 23.67%). The maximum adsorption capacities were found as ordered, MG (46.387 mg/g) > MB (23.154 mg/g) > BB (22.8 mg/g) > CR dye (11.063 mg/g). Through the intra-particle diffusion kinetic model, MG and BB adsorption endured a three-step process, while CR and MB adsorption was a two-step process. The recyclability of the green CuO@C nanocomposite was three cycles with 67.54% for the final cycle of BB removal. Moreover, the nanoadsorbent displayed a high stability, checked by X-ray diffraction, FT-IR analysis, EDX spectra, and SEM images. It is recommended that the green CuO@C nanocomposite biosynthesized using the Combretum indicum flower extract can be a good alternative for the dye treatment from wastewater.

Fe3O4-chitosan nanocomposite as a magnetic biosorbent for removal of nickel and cobalt heavy metals from polluted water

Recently, natural polymers like chitosan have gained attention as promising adsorbents for water treatment. By combining chitosan with magnetic nanoparticles, their adsorption capabilities can be enhanced. In this study, chitosan-magnetite nanocomposite (CMNC) was synthesized via coprecipitation method to remove nickel and cobalt from aqueous solutions. The physicochemical properties of the synthesized CMNC were investigated by various techniques, including FESEM, TEM, XPS, FTIR, XRD, and VSM. The electron microscopy results confirmed the uniform dispersion of magnetite nanoparticles within CMNC nanocomposites, while VSM confirmed their significant magnetic properties. The adsorption experiments showed that at optimal conditions (pH = 6, contact time = 2 h, adsorbent dosage = 2 g/l), CMNC has high adsorption capacities of 30.03 mg/g for Ni2+ and 53.19 mg/g for Co2+. Furthermore, the adsorption data fitted best with the Langmuir isotherm, show that the active sites on CMNC are energetically homogenous. According to kinetic analysis, the experimental data were in good agreement with both pseudo-second-order and intra-particle diffusion models, which suggest that chemical sorption, along with mass transfer steps, influence the overall adsorption process. Finally, investigating the thermodynamic parameters (∆Gads, ∆Hads, ∆Sads) showed that the adsorption process on CMNC was endothermic and spontaneous, with stronger interactions observed between CMNC and Co2+ compared to Ni2+.

Chitosan Hydrogels for Water Purification Applications

Chitosan-based hydrogels have gained significant attention for their potential applications in water treatment and purification due to their remarkable properties such as bioavailability, biocompatibility, biodegradability, environmental friendliness, high pollutants adsorption capacity, and water adsorption capacity. This article comprehensively reviews recent advances in chitosan-based hydrogel materials for water purification applications. The synthesis methods, structural properties, and water purification performance of chitosan-based hydrogels are critically analyzed. The incorporation of various nanomaterials into chitosan-based hydrogels, such as nanoparticles, graphene, and metal-organic frameworks, has been explored to enhance their performance. The mechanisms of water purification, including adsorption, filtration, and antimicrobial activity, are also discussed in detail. The potential of chitosan-based hydrogels for the removal of pollutants, such as heavy metals, organic contaminants, and microorganisms, from water sources is highlighted. Moreover, the challenges and future perspectives of chitosan-based hydrogels in water treatment and water purification applications are also illustrated. Overall, this article provides valuable insights into the current state of the art regarding chitosan-based hydrogels for water purification applications and highlights their potential for addressing global water pollution challenges.

Recent advances in nanomaterials based sustainable approaches for mitigation of emerging organic pollutants

Emerging organic pollutants (EOPs) are a category of pollutants that are relatively new to the environment and recently garnered a lot of attention. The majority of EOPs includes endocrine-disrupting chemicals (EDCs), antibiotic resistance genes (ARGs), pesticides, dyes and pharmaceutical and personal care products (PPCPs). Exposure to contaminated water has been linked to an increase in incidences of malnutrition, intrauterine growth retardation, respiratory illnesses, liver malfunctions, eye and skin diseases, and fatalities. Consequently, there is a critical need for wastewater remediation technologies which are effective, reliable, and economical. Conventional wastewater treatment methods have several shortcomings that can be addressed with the help of nanotechnology. Unique characteristics of nanomaterials (NMs) make them intriguing and efficient alternative in wastewater treatment strategies. This review emphasis on the occurrence of divers emerging organic pollutants (EOPs) in water and their effective elimination via different NMs based methods with in-depth mechanisms. Furthermore, it also delves the toxicity assessment of NMs and critical challenges, which are crucial steps for practical implementations.

Chitosan-Grafted Polyacrylic Acid-Doped Copper Oxide Nanoflakes Used as a Potential Dye Degrader and Antibacterial Agent: In Silico Molecular Docking Analysis

This study examined the catalytic and bactericidal properties of polymer-doped copper oxide (CuO). For this purpose, a facile co-precipitation method was used to synthesize CuO nanostructures doped with CS-g-PAA. Various concentrations (2, 4, and 6%) of dopants were systematically incorporated into a fixed amount of CuO. The prepared samples were analyzed by different optical, structural, and morphological characterizations. Field emission scanning electron microscopy and transmission electron microscopy micrographs indicated that doping transformed CuO's agglomerated rod-like surface morphology to form nanoflakes. UV-vis spectroscopy revealed that the optical spectra of the samples exhibit a redshift after doping, leading to a decrease in band gap energy from 3.3 to 2.5 eV. The purpose of the study was to test the catalytic activity of pristine and CS-g-PAA doped CuO for the degradation of methylene blue in acidic, basic, and neutral conditions using NaBH₄ as a reducing agent in an aqueous medium. Furthermore, antibacterial activity was evaluated against Gram-positive and Gram-negative bacteria, namely, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Overall, enhanced bactericidal performance was observed upon doping CS-g-PAA into CuO, i.e., 4.25-6.15 and 4.40-8.15 mm against S. aureus and 1.35-4.20 and 2.25-5.25 mm against E. coli at the lowest and highest doses, respectively. The relevant catalytic and bactericidal action mechanisms of samples are also proposed in the study. Moreover, in silico molecular docking studies illustrated the role of these prepared nanomaterials as possible inhibitors of FabH and FabI enzymes of the fatty acid biosynthetic pathway.

Immobilized Nanomaterials for Environmental Applications

Nanomaterials (NMs) have been extensively used in several environmental applications; however, their widespread dissemination at full scale is hindered by difficulties keeping them active in engineered systems. Thus, several strategies to immobilize NMs for their environmental utilization have been established and are described in the present review, emphasizing their role in the production of renewable energies, the removal of priority pollutants, as well as greenhouse gases, from industrial streams, by both biological and physicochemical processes. The challenges to optimize the application of immobilized NMs and the relevant research topics to consider in future research are also presented to encourage the scientific community to respond to current needs.

Review on some metal oxide nanoparticles as effective adsorbent in wastewater treatment

Water contamination has turned into one of the most serious issues in the world. Nanomaterials are proficient to carry away heavy metals, organic and inorganic dyes, pesticides, and small molecules from polluted water. In this regard, nanoparticles have gained much attention due to their extraordinary properties compared to bulk materials. Metal oxide nanoparticles and nanocomposites have several advantages such as elevated surface area, low concentration, easily separable after treatment and so on. Among many feasible techniques, the adsorption process is one of the most useful techniques for removing heavy ions and dyes from wastewater and has gained much attention from researchers. Several studies on metal oxide nanoparticles and their use in wastewater treatment have been published in the literature. This chapter gives an outline about five metal oxide based nanomaterials and nanocomposites as well as their applications in water pollution removal where the efficiency, limits and favourable circumstances are compared and explored. This article surely helps to gather information about some metal oxide nanoparticles and nanocomposites in wastewater treatment by the adsorption technique. In this review article, we primarily focused on five metal oxide nanoparticles and some of their recent applications published in the last two years.

Advances in Amine-Surface Functionalization of Inorganic Adsorbents for Water Treatment and Antimicrobial Activities: A Review

In the last decade, adsorption has exhibited promising and effective outcomes as a treatment technique for wastewater contaminated with many types of pollutants such as heavy metals, dyes, pharmaceuticals, and bacteria. To achieve such effectiveness, a number of potential adsorbents have been synthesized and applied for water remediation and antimicrobial activities. Among these inorganic adsorbents (INAD), activated carbon, silica, metal oxide, metal nanoparticles, metal–organic fibers, and graphene oxide have been evaluated. In recent years, significant efforts have been made in the development of highly efficient adsorbent materials for gas and liquid phases. For gas capture and water decontamination, the most popular and known functionalization strategy is the chemical grafting of amine, due to its low cost, ecofriendliness, and effectiveness. In this context, various amines such as 3-aminopropyltriethoxysilane (APTES), diethanolamine (DEA), dendrimer-based polyamidoamine (PAMAM), branched polyethyleneimine (PEI), and others are employed for the surface modification of INADs to constitute a large panel of resource and low-cost materials usable as an alternative to conventional treatments aimed at removing organic and inorganic pollutants and pathogenic bacteria. Amine-grafted INAD has long been considered as a promising approach for the adsorption of both inorganic and organic pollutants. The goal of this review is to provide an overview of surface modifications through amine grafting and their adsorption behavior under diverse conditions. Amine grafting strategies are investigated in terms of the effects of the solvent, temperature, and the concentration precursor. The literature survey presented in this work provides evidence of the significant potential of amine-grafted INAD to remove not only various contaminants separately from polluted water, but also to remove pollutant mixtures and bacteria.

Immobilized enzymes and cell systems: an approach to the removal of phenol and the challenges to incorporate nanoparticle-based technology

The presence of phenol in wastewater poses a risk to ecosystems and human health. The traditional processes to remove phenol from wastewater, although effective, have several drawbacks. The best alternative is the application of ecological biotechnology tools since they involve biological systems (enzymes and microorganisms) with moderate economic and environmental impact. However, these systems have a high sensitivity to environmental factors and high substrate concentrations that reduce their effectiveness in phenol removal. This can be overcome by immobilization-based technology to increase the performance of enzymes and bacteria. A key component to ensure successful immobilization is the material (polymeric matrices) used as support for the biological system. In addition, by incorporating magnetic nanoparticles into conventional immobilized systems, a low-cost process is achieved but, most importantly, the magnetically immobilized system can be recovered, recycled, and reused. In this review, we study the existing alternatives for treating wastewater with phenol, from physical and chemical to biological techniques. The latter focus on the immobilization of enzymes and microorganisms. The characteristics of the support materials that ensure the viability of the immobilization are compared. In addition, the challenges and opportunities that arise from incorporating magnetic nanoparticles in immobilized systems are addressed.

Polymeric Nanocomposites for Environmental and Industrial Applications

Polymeric nanocomposites (PNC) have an outstanding potential for various applications as the integrated structure of the PNCs exhibits properties that none of its component materials individually possess. Moreover, it is possible to fabricate PNCs into desired shapes and sizes, which would enable controlling their properties, such as their surface area, magnetic behavior, optical properties, and catalytic activity. The low cost and light weight of PNCs have further contributed to their potential in various environmental and industrial applications. Stimuli-responsive nanocomposites are a subgroup of PNCs having a minimum of one promising chemical and physical property that may be controlled by or follow a stimulus response. Such outstanding properties and behaviors have extended the scope of application of these nanocomposites. The present review discusses the various methods of preparation available for PNCs, including in situ synthesis, solution mixing, melt blending, and electrospinning. In addition, various environmental and industrial applications of PNCs, including those in the fields of water treatment, electromagnetic shielding in aerospace applications, sensor devices, and food packaging, are outlined.