Removal of direct dyes from aqueous solution by oxidized starch cross-linked chitosan/silica hybrid membrane

Innovative biopolyelectrolytes-based technologies for wastewater treatment

Developing eco-friendly, cost-effective, and efficient methods for treating water pollutants has become paramount in recent years. Biopolyelectrolytes (BPEs), comprising natural polymers like chitosan, alginate, and cellulose, have emerged as versatile tools in this pursuit. This review offers a comprehensive exploration of the diverse roles of BPEs in combating water contamination, spanning coagulation-flocculation, adsorption, and filtration membrane techniques. With ionizable functional groups, BPEs exhibit promise in removing heavy metals, dyes, and various pollutants. Studies showcase the efficacy of chitosan, alginate, and pectin in achieving notable removal rates. BPEs efficiently adsorb heavy metal ions, dyes, and pesticides, leveraging robust adsorption capacity and exceptional mechanical properties. Furthermore, BPEs play a pivotal role in filtration membrane techniques, offering efficient separation systems with high removal rates and low energy consumption. Despite challenges related to production costs and property variability, their environmentally friendly, biodegradable, renewable, and recyclable nature positions BPEs as compelling candidates for sustainable water treatment technologies. This review delves deeper into BPEs' modification and integration with other materials; these natural polymers hold substantial promise in revolutionizing the landscape of water treatment technologies, offering eco-conscious solutions to address the pressing global issue of water pollution.

Efficient adsorption of azo anionic dye Congo Red by micro-nano metal-organic framework MIL-68(Fe) and MIL-68(Fe)/chitosan composite sponge: Preparation, characterization and adsorption performance

Micro-nano metal-organic framework (MIL-68(Fe)) for efficient adsorption of azo anionic dye Congo red (CR) was successfully prepared by one-step hydrothermal method under acidic environment. And a MIL-68(Fe)/chitosan composite sponge (MIL-68(Fe)/CS) was prepared under the coating of chitosan (CS). After comparing the performance of MIL-68(Fe) and MIL-68(Fe)/CS, we focus on exploring MIL-68(Fe)/CS. It ensured the CR removal efficiency while reaching the adsorption equilibrium faster than MIL-68(Fe), and solved the defect that the powder was difficult to be stripped by water after adsorption. The physicochemical properties and surface morphology of the adsorbent were characterized by SEM, FTIR, XRD, TGA, BET, and Zeta potential. The effects of pH, contact time, adsorbent dosage, initial solution concentration and temperature on the adsorption performance of the adsorbent were systematically analyzed. The pseudo-second-order model and the Sips model were most consistent for the adsorption process, indicating that the adsorption process of MIL-68(Fe)/chitosan composite sponge on CR is a complex physicochemical process. The removal rates of CR by MIL-68(Fe) and MIL-68(Fe)/chitosan composite sponge reached the maximum values of 99.55 % and 99.51 % at 318 K, respectively. And the maximum adsorption capacity of CR by MIL-68(Fe)/chitosan composite sponge at 318 K was 1184.16 mg·g-1. After six cycles of adsorption and desorption, the removal rate of CR was still higher than 80 %. The synergistic effects of π-π stacking, electrostatic interactions, hydrogen bonding and pore filling have important effects on CR removal.

Adsorption of antibiotics by bentonite-chitosan composite: Phenomenological modeling and physical investigation of the adsorption process

The increased use of antibiotics worldwide turned into a serious preoccupation due to their environmental and health impacts. Since the majority of antibiotic residuals are hardly eliminated from wastewater, based on usual methods, other treatments receive considerable attention. Adsorption is known as the most effective method of the treatment of antibiotics. In this paper, the adsorption isotherms of doripenem, ampicillin, and amoxicillin on bentonite-chitosan composite are determined at three temperatures, T = 303.15, 313.15 and 323.15 K, which are used to achieve a theoretical investigation of the removal phenomenon, based on a statistical physics theory. Three analytical models are utilized to describe the AMO, AMP, and DOR adsorption phenomena at the molecular level. From the fitting results, all antibiotic adsorption on a BC adsorbent is associated with the monolayer formation with one type of site. Concerning the number of adsorbed molecules per site (n), it is concluded that multi-docking (n < 1) and multi-molecular (n > 1) phenomena are feasible for AMO, AMP, and DOR adsorption on BC. The adsorption amounts at saturation of the BC adsorbent, deduced by the monolayer model, are found to be 70.4-88.0 mg/g for doripenem, 57.8-79.2 mg/g for ampicillin and 38.6-67.5 mg/g for amoxicillin indicating that the antibiotics adsorption performance of BC was greatly depended on temperature where the adsorption capacities increased with the increment of this operating variable. All adsorption systems are demonstrated by a calculation of the energy of adsorption, considering that the extrication of these pollutants implies physical interactions. The thermodynamic interpretation confirms the spontaneous and feasible nature of the adsorption of the three antibiotics on BC adsorbent. In brief, BC sample is regarded as a promising adsorbent to extract antibiotics from water and presents important potentials to be effected in wastewater handling at industrial level.

Synthesis and Characterization of Terbium-Based Metal Organic Framework for Environmental Remediation Application

In the present study, terbium-based metal-organic frameworks (MOFs) based on fcu topology, fcu-Tb- FTZB-MOF, was synthesized using 2-fluoro-4-(1H-tetrazol-5-yl)benzoic acid (FTZB) as a linear ligand, and then was characterized using powder X-ray diffraction (PXRD) and Brunauer-Emmett-Teller (BET) analysis and to study the texture properties of the Tb-FTZB-MOF. The characterization results confirmed the successful synthesis of the high surface area Tb-FTZB-MOF (1220 m2/g). The synthesized Tb-FTZB-MOF was then applied as a catalytic adsorbent to remove direct violet 31 (DV31) dye as an example of organic pollutants, from a model and real solution. The effect of various operational parameters such as adsorbent loading, contact time, initial DV31 dye concentration, initial solution pH, different water matrix, temperature, and ionic strength have also been evaluated. Solution pH and temperature significantly influenced the adsorption of DV31 dye using Tb-FTZB-MOF, and the results should efficiently remove the DV31 dye at ambient temperature, and at pH value of 8.0 using 35 mg Tb-FTZB-MOF, within few minutes. The process was studied kinetically and found to follow the pseudo-second-order kinetic model, and thermodynamically the process was spontaneous, endothermic, with a positive entropy. Finally, the result showed that Tb-FTZB-MOF was able to adsorb a high percentage of DV31 dye and maintained reasonable efficiency even after five cycles, indicating that Tb-FTZB-MOF could be a promising adsorbent in wastewater remediation.

Construction of a cellulose-based high-performance adhesive with a crosslinking structure bridged by Schiff base and ureido groups

Biomass-based adhesives are considered to be the preferred alternative to formaldehyde-type wood adhesives due to their wide range of sources, low cost, and sustainability. Herein, an environmentally friendly Schiff base cross-linked compact three-dimensional network structure bio-adhesive (DAC-PEI-U) derived from polyethyleneimine (PEI), urea, and cellulose was successfully prepared, verifying by detailed FTIR, NMR, and XPS analysis. Schiff base bridging between aldehyde groups in dialdehyde cellulose (DAC) and amino groups in polyurea (PEIU) not only constructed crosslinking networks but also endowed adhesives with good adhesion property. The dry bond strength of DAC-PEI-U adhesive reached 2.71 MPa, and the wet shear strength was 1.51 MPa (hot water) and 1.34 MPa (boiling water), respectively. It not only improves the water resistance and bonding process, but also displays simple synthesis and low cost. The improved performance of DAC-PEI-U adhesive is attributed to the generation of hyperbranched cross-linking structure in the adhesive system, which results in increased cross-linking density and promotes the formation of dense cross-sections in the curing adhesive. This work paves a solid way for developing cellulose-based wood adhesives with wet bonding properties, thus holding great potential as an alternative to formaldehyde-type adhesives in wood-based panel and indoor panel bonding industries.

Recent Developments in the Removal of Dyes from Water by Starch-Based Adsorbents

Starch-based adsorbents have demonstrated excellent potential for the removal of various noxious dyes from wastewater. This review critically evaluates the recent progress in applications of starch-based adsorbents for the removal of dyes from water. The synthesis methods of starch-based composites and their effects on physicochemical characteristics of produced adsorbents are discussed. The removal of various dyes by starch-based adsorbents are described in detail, with emphasis on the effect of key parameters, adsorption mechanism and their reusability potential. The key challenges related to the synthesis and applications of starch-based adsorbents in water purification are highlighted. Based on the research gaps, recommendations for future research are made. The evaluation of starch-based adsorbents would contribute to the development of sustainable water treatment options in near future.

Hydroxyapatite-based adsorbents: Applications in sequestering heavy metals and dyes

Hydroxyapatite (HAp) is a calcium phosphate material that was used primarily in bone regeneration and repair as a result of its chemical similarity with bone. However, HAp has emerged as a very promising adsorbent for sequestering contaminants like heavy metals, dyes, hydrocarbons as well as other emerging pollutants from wastewater as a result of its versatility and encouraging adsorptive properties. Contaminants like heavy metals and dyes have been a major source of environmental concern. Research studies involving the use of HAp as adsorbents for the adsorptive treatment of heavy metal- and dye-contaminated wastewater have become increasingly popular due to its eco-friendliness, easy synthesis, unique adsorption properties etc. Various methods are available for the synthesis of HAp and its composites with some of these methods used in combination with other methods to obtain more efficient HAp-based adsorbents. In this work, the adsorptive removal of heavy metals and dyes by HAp and its composites was extensively reviewed as well as the parametric effects of process factors like contact time, solution pH, temperature, solute concentration etc on the adsorption process. Kinetic, thermodynamic, and isotherm models for elucidating the adsorption process were also considered. Generally, from the works reviewed, HAp-based adsorbents were found to be very effective for sequestering heavy metals and dyes from solution and thus presents a low-cost option for adsorptive wastewater treatment.

Recent Advances in Biopolymeric Membranes towards the Removal of Emerging Organic Pollutants from Water

Herein, this paper details a comprehensive review on the biopolymeric membrane applications in micropollutants' removal from wastewater. As such, the implications of utilising non-biodegradable membrane materials are outlined. In comparison, considerations on the concept of utilising nanostructured biodegradable polymeric membranes are also outlined. Such biodegradable polymers under considerations include biopolymers-derived cellulose and carrageenan. The advantages of these biopolymer materials include renewability, biocompatibility, biodegradability, and cost-effectiveness when compared to non-biodegradable polymers. The modifications of the biopolymeric membranes were also deliberated in detail. This included the utilisation of cellulose as matrix support for nanomaterials. Furthermore, attention towards the recent advances on using nanofillers towards the stabilisation and enhancement of biopolymeric membrane performances towards organic contaminants removal. It was noted that most of the biopolymeric membrane applications focused on organic dyes (methyl blue, Congo red, azo dyes), crude oil, hexane, and pharmaceutical chemicals such as tetracycline. However, more studies should be dedicated towards emerging pollutants such as micropollutants. The biopolymeric membrane performances such as rejection capabilities, fouling resistance, and water permeability properties were also outlined.

Research progress of adsorption and removal of heavy metals by chitosan and its derivatives: A review

Chitosan has received widespread attention as an adsorbent for pollutants because of its low cost and great adsorption potentials. Chitosan has abundant hydroxyl and amino groups that can bind heavy metal ions. However, it has defects such as sensitivity to pH, low thermal stability, and low mechanical strength, which limit the application of chitosan in wastewater treatment. The functional groups of chitosan can be modified to improve its performance via crosslinking and graft modification. The porosity and specific surface area of chitosan in powder form are not ideal, therefore, physical modification has been attempted to generate chitosan nanoparticles and hydrogel. Chitosan has also been integrated with other materials (e.g. graphene, zeolite) resulting in composite materials with improved adsorption performance. This review mainly focuses on reports about the application of chitosan and its derivatives to remove different heavy metals. The preparation strategy, adsorption mechanism, and factors affecting the adsorption performance of adsorbents for each type of heavy metal are discussed in detail. Recent reports on important organic pollutants (dyes and phenol) removal by chitosan and its derivatives are also briefly discussed.

Binary coagulation system (graphene oxide/chitosan) for polluted surface water treatment

In this study, chitosan (CS) is used as a natural coagulant aid alongside graphene oxide (GO) to remove turbidity and numerous pollutants from raw and artificially contaminated surface water. The coagulation capability of the system (GO/CS) was assessed with respect to a water sample's turbidity, pH, coagulant dose, settling velocity, and temperature. The presence of CS enhanced the coagulation capacity of GO at varied pH levels and no GO residue was detected in the water after the treatment. The proposed system achieved high turbidity removal efficiency (≥98.3%) for all turbidity levels. A mixture of GO (8 mg/L) and CS (2 mg/L) was ideal to remove algae (99.5%) and bacteria (≥95.0%). Furthermore, it demonstrated a high coagulation capacity to remove dyes, direct brown-2 (DB-2), methylene blue (MB), and Pb(II) ions from artificially contaminated surface water. Interestingly, the sludge exhibited an extraordinary adsorption capacity for DB-2, MB, and Pb(II) ions. The adsorption process followed the pseudo-second-order kinetic model, and was consistent with the Langmuir model, with an adsorption capacity of up to 667.8, 400.7, and 459.1 mg/g for DB-2, MB, and Pb(II) ions, respectively. Therefore, the presented binary coagulation system is of great potential economic value for the treatment of raw surface water and wastewater.

Examining the Impact of Squaric Acid as a Crosslinking Agent on the Properties of Chitosan-Based Films

Hydrogels based on chitosan are very versatile materials which can be used for tissue engineering as well as in controlled drug delivery systems. One of the methods for obtaining a chitosan-based hydrogel is crosslinking by applying different components. The objective of the present study was to obtain a series of new crosslinked chitosan-based films by means of solvent casting method. Squaric acid-3,4-dihydroxy-3-cyclobutene-1,2-dione-was used as a safe crosslinking agent. The effect of the squaric acid on the structural, mechanical, thermal, and swelling properties of the formed films was determined. It was established that the addition of the squaric acid significantly improved Young's modulus, tensile strength, and thermal stability of the obtained materials. Moreover, it should be stressed that the samples consisting of chitosan and squaric acid were characterized by a higher swelling than pure chitosan. The detailed characterization proved that squaric acid could be used as a new effective crosslinking agent.

Bio-crosslinking of chitosan with oxidized starch, its functionalization with amino acid and magnetization: As a green magnetic support for silver immobilization and its catalytic activity investigation

In this study, we have reported the synthesis and characterization of new magnetic bionanocatalyst based on chitosan and investigated their catalytic activity in the A³-coupling reaction. In order to increase the stability of chitosan, starch oxide biopolymer was used as a green covalent linking agent between chitosan chains. After the cross-linking of chitosan with starch oxide, aldehyde functional groups were reacted with amine groups of cysteine to form the corresponding Schiff bases in the hybrid biopolymer. Then, the imine bonds were reduced to prevent possible their hydrolysis. The magnetic support was resulted with addition of iron oxide nanoparticles. In the presence of thiol and carboxylate coordinated groups of amino acid, silver ions were immobilized on this biosupport.

Polymeric nanocomposites for the removal of Acid red 52 dye from aqueous solutions: Synthesis, characterization, kinetic and isotherm studies

Polymeric nanocomposites polyaniline-polyvinylpyrrolidone (PAPV) and polyaniline-polyvinylpyrrolidone-neodymium/zinc oxide (PAPV-NZO) were synthesized for the effective dye removal through adsorption process. Neodymium doped zinc oxide (NZO) with various proportions of neodymium were prepared by chemical co-precipitation method and incorporated into the copolymer matrix via oxidative polymerization technique. NZO nanoparticles were characterized by X-ray diffraction (XRD) and the morphological features, and functional group linkages of the PAPV-NZO were confirmed by scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) analyses. Acid red 52 dye was chosen as a synthetic toxic effluent to study the removal efficiency of the nanocomposites with different parameters viz. time, concentration, adsorbent dosage and pH. The studies were performed under visible light irradiation and the residual dye concentration was analyzed by UV-visible spectrophotometer. PAPV-NZO exhibited greater dye removal rate than PAPV due to the incorporation of NZO that enhanced the conducting nature, stability and surface area of PAPV-NZO. The optimum concentration of the dye and the adsorbent dosage of the PAPV-NZO were determined to be 80 ppm and 50 mg, respectively. At acidic condition of pH 2, the removal capacity of PAPV-NZO was found 99.6%. Kinetic and isotherm models have been studied on the optimum parameters to investigate the nature of the adsorption process. The process followed pseudo second order kinetics and was best suited to the Langmuir model. The maximum dye adsorption capacity of PAPV-NZO was estimated to be 159.36 mg g^-1. From the results, it can be assured that the PAPV-NZO can be effectively used for the removal of dye pollutants in water.

Porous chitosan/hydroxyapatite composite membrane for dyes static and dynamic removal from aqueous solution

The unique characteristics of Chitosan (CS) such as resource abundance, good biocompatibility, film-forming ability and sufficient sites (NH₂ and OH) for adsorption of heavy metals or organic pollutants make CS-based membranes a promising membrane adsorbent. In this work, a porous Chitosan/Hydroxyapatite (CS/HA) membrane with a sponge-like surface and a three-dimensional interpenetrated porous structure of about mean pore size less than 10μm was developed. The most striking advantage of the proposed membrane lies on the integration of appreciably high adsorption capacity (as compared with current CS-based membranes, also 2.5 times and 4 times higher than that of non-porous CS/HA membrane and the commercially available activate carbon) and the high-speed dynamic dye removal (98% or even better in less than 15min). Besides, the synthesis protocol for the proposed membrane is also much simpler, environmental-friendly and economical. Moreover, the proposed membrane also featured repeated dye removal (above 80% after 5 cycles of dynamic adsorption at dye concentration of 150mgL^-1). All the above advantages indicated the intriguing potential of the porous membrane in practical wastewater treatment.

Preparation of a regenerated silk fibroin film and its adsorbability to azo dyes

In this work, a novel and sustainable biosorbent, regenerated silk fibroin film (rSFF) was successfully prepared and its adsorbability to azo dyes (acid yellow 11, naphthol orange and direct orange S) was measured. At optimal conditions, the adsorption capacity of rSFF for acid yellow 11 reached up to 59.71mg/g, which was 1.23-fold higher than that of raw silk fibroin fibers. More importantly, rSFF exhibited a high level of flexibility and functionality as well as a good shaping ability, which were crucial for its practical application. The SEM results showed that rSFF was a porous material, indicating that it had more available adsorption sites compared with raw silk fibroin fibers, which might contribute to the higher adsorption capacity of rSFF. Isotherm equilibrium studies revealed that the azo dye adsorption process followed the Langmuir model, indicating that rSFF was a structurally homogenous adsorbent. The recycle test showed that rSFF had potential to be reused in a number of treatment cycles. After five cycles, its adsorbability to acid yellow 11 remained as high as 47.20mg/g. Finally, a scale-up experiment was performed for rSFF, and the results indicated that it was feasible for rSFF to extend the practical application.

Novel amphiphilic glucose-responsive modified starch micelles for insulin delivery

Glucose-responsive micelles with Schiff-based was reported, which had excellent stability and biocompatibility. The release of the insulin accelerated in high glucose concentration due to the highly sensitive of glucose in physiological conditions.