Efficient Removal of Acidic Dye Using Low-Cost Biocomposite Beads

Mussel-Inspired Magnetic Dissolving Pulp Fibers Toward the Adsorption and Degradation of Organic Dyes

In this work, a simple synthetic method was used to prepare a new type of magnetic dissolving pulp (MDP) @polydopamine (PDA) fibers. The hydroxyl groups of the fibers were converted into carboxyl groups after succinylation. Fe₃O₄ nanoparticles were grown in situ on the fibers. The prepared MDP@PDA fibers have catalytic reduction efficiency and adsorption performance for methylene blue organic dyes, and it has been thoroughly tested under various pH conditions. Fe₃O₄@PDA fibers have high reusability, are easy to separate, and regenerate quickly. The catalytic and adsorption efficiency barely decreases after repeated use. The surface of dissolving pulp fibers with a functionalized multifunctional PDA coating is used to create multifunctional catalysts and adsorbent materials. This study presents a very useful and convenient method for the synthesis and adjustment of MDP@PDA fibers, which have a wide range of potential applications in catalysis and wastewater treatment.

A State-of-the-Art Review on Biowaste Derived Chitosan Biomaterials for Biosorption of Organic Dyes: Parameter Studies, Kinetics, Isotherms and Thermodynamics

Chitosan is a second-most abundant biopolymer on earth after cellulose. Its unique properties have recently received particular attention from researchers to be used as a potential biosorbent for the removal of organic dyes. However, pure chitosan has some limitations that exhibit lower biosorption capacity, surface area and thermal stability than chitosan composites. The reinforcement materials used for the synthesis of chitosan composites were carbon-based materials, metal oxides and other biopolymers. This paper reviews the effects of several factors such as pH, biosorbent dosage, initial dye concentration, contact time and temperature when utilizing chitosan-based materials as biosorbent for removing of organic dyes from contaminated water. The behaviour of the biosorption process for various chitosan composites was compared and analysed through the kinetic models, isotherm models and thermodynamic parameters. The findings revealed that pseudo-second-order (PSO) and Langmuir isotherm models were best suited for describing most of the biosorption processes or organic dyes. This indicated that monolayer chemisorption of organic dyes occurred on the surface of chitosan composites. Most of the biosorption processes were endothermic, feasible and spontaneous at the low temperature range between 288 K and 320 K. Therefore, chitosan composites were proven to be a promising biosorbent for the removal of organic dyes.

Coal bottom ash derived zeolite (SSZ-13) for the sorption of synthetic anion Alizarin Red S (ARS) dye

SSZ-13 zeolite was successfully synthesized from coal bottom ash (CBA) upon hydrothermal treatment for selective sorption of Alizarin Red S (ARS) dye. The characterization of CBA, and SSZ-13 were performed using BET, SEM, FTIR, XRF, and XRD techniques. The optimal fusion ratio (CBA: NaOH) was identified as 1:3, resulting zeolite SSZ-13 with a specific surface area of 206.6 m²/g, compared to raw CBA (7.81 m²/g). The kinetics, isotherms, and thermodynamics of the ARS adsorption onto the SSZ-13, and CBA were assessed under various conditions. The results indicated that the adsorption phenomenon is optimal under acidic medium (pH = 2 for CBA, pH = 3 for SSZ-13); at ambient room temperature of 298 K; adsorbent dosage of 0.03 g, contact time of 120 min. Further, the equilibrium data fitted well to Langmuir isotherm (q_e = 210.75 mg/g), following pseudo-second-order kinetics. Moreover, the chemisorption phenomenon is clearly described using Elovich kinetic model. Various thermodynamic parameters signifies the adsorption phenomenon is spontaneous, and endothermic in nature. Finally, regeneration studies revealed the sensitivity of SSZ-13 zeolite towards 0.1 M NaOH/EtOH eluent in recovery and the possibility of reuse to five successive adsorption/desorption cycles. Thus, hydrothermal treatment of CBA has potential in producing zeolites suitable to adsorption.

Cellulose-Based Hydrogels for Wastewater Treatment: A Concise Review

Finding affordable and environment-friendly options to decontaminate wastewater generated with heavy metals and dyes to prevent the depletion of accessible freshwater resources is one of the indispensable challenges of the 21st century. Adsorption is yet to be the most effective and low-cost wastewater treatment method used for the removal of pollutants from wastewater, while naturally derived adsorbent materials have garnered tremendous attention. One promising example of such adsorbents is hydrogels (HGs), which constitute a three-dimensional polymeric network of hydrophilic groups that is highly capable of adsorbing a large quantity of metal ions and dyes from wastewater. Although HGs can also be prepared from synthetic polymers, natural polymers have improved environmental benignity. Recently, cellulose-based hydrogels (CBHs) have been extensively studied owing to their high abundance, biodegradability, non-toxicity, and excellent adsorption capacity. This review emphasizes different CBH adsorbents in the context of dyes and heavy metals removal from wastewater following diverse synthesis techniques and adsorption mechanisms. This study also summarizes various process parameters necessary to optimize adsorption capacity followed by future research directions.

An in vitro evaluation of zinc silicate fortified chitosan scaffolds for bone tissue engineering

Tissue engineering aims at replacement, repair, and regeneration of tissues by a combination of scaffolds, growth factors, and cells. In this study, we report the synthesis of biodegradable composite scaffolds fortified with mesoporous zinc silicate (mZS) and assessment of in vitro properties for bone tissue engineering (BTE) applications. The scaffolds consisted of chitosan (CS) incorporated with mZS at 0.1, 0.2, 0.3, and 0.5 wt%. The bio-composite scaffolds were visualized using Field Emission Scanning Electron Microscopy (FE-SEM). The incorporation of mZS was confirmed using Energy dispersive x-ray (EDS) analysis. Biomineralization studies were conducted in simulated body fluid (SBF) and indicated bioactivity of fabricated scaffolds. The scaffolds also displayed antibacterial action against Staphylococcus aureus. Cellular attachment within the scaffold network established biocompatibility of the material. Incorporation of mZS within the chitosan scaffolds matrix improved properties such as porosity, degradation rate, and biomineralization. Therefore, fabricated scaffolds exhibit exceptional features and have the potential to serve as an implant for BTE applications.

Composites for wastewater purification: A review

The review deals with different kinds of composites which have been used for wastewater treatment. The use of different types of composites ranging from nanocomposites, activated charcoal composites, polymer composites, oxide-based composites, hybrid composites, and biosorbent composites, etc. has been dealt with in detail, and presented as a central source of knowledge. The paper incorporates water purification explicitly via adsorption process, which has proven to be economical and efficient. These composites have been explored for treating or elimination of various hazardous substances like heavy metal species, different classes of colored contaminants (dyes), several organic and inorganic pollutants from wastewater. The composites discussed have successfully eliminated Zn²⁺, Ni²⁺, Cu²⁺, Pb²⁺, Hg, etc. In some instances the removal percentage of the contaminants was almost 100%. The presented data reveals the efficiency of composite materials in wastewater treatment over the conventional singular materials.

Polyaniline and sodium alginate nanocomposite: a pH-responsive adsorbent for the removal of organic dyes from water

pH-responsive adsorbents are promising tools in water remediation as they possess selective adsorption towards cationic and anionic dyes, which can be controlled by varying the pH of the medium. In this study, a pH-responsive nanocomposite of polyaniline–sodium alginate (PANI/SA) was synthesized. The composite was found to be an efficient adsorbent for the removal of both cationic and anionic dyes from water at different pH values. The extent of adsorption was evaluated as a function of initial dye concentration, solution pH, temperature, contact time, dose of adsorbent and coexisting ions. The detailed investigation of kinetics and adsorption isotherm showed that the dyes adsorbed in accordance with pseudo-second order kinetic and Langmuir adsorption isotherms. The maximum adsorption capacities of the nanocomposite for Methylene blue (MB), Rhodamine B (RB), Orange-II (O-II), and Methyl orange (MO) dyes were found to be 555.5 mg g⁻¹, 434.78 mg g⁻¹, 476.19 mg g⁻¹, and 416.66 mg g⁻¹, respectively, which is higher compared to other reported adsorbents. The feasibility of the adsorption process was ascertained from thermodynamic parameters.

Polyaniline and sodium alginate nanocomposite was synthesized and it was used for selective removal of both cationic and anionic dyes from water at different pH.

Novel cellulose/montmorillonite mesoporous composite beads for dye removal in single and binary systems

Fine aminated cellulose/montmorillonite mesoporous composite beads (ACeMt) were prepared as green-based adsorbent via a novel approach utilizing ultra-fine calcium carbonate as a pore-forming agent to increase the porosity and specific surface area of ACeMt. The resulting bioadsorbent was characterized by means of SEM, FTIR and BET analysis and used for dye removal. Adsorption experimental data were fitted with various isotherm and kinetic models. The results indicated that chemical adsorption was the rate-limiting step. The maximum adsorption capacities of ACeMt, better described by Langmuir model, were much higher than those of conventional adsorbents, particularly for the removal of Auramine O dye (up to 1336.2 mg/g at 55 °C). The adsorptions at equilibrium were better correlated with Redlich-Peterson model and uncompetitive Langmuir isotherm model in single and binary system, respectively. Overall, ACeMt is a promising bioadsorbent and highly efficient in the removal of dyes for water clarification.

Biopolymer-Grafted, Magnetically Tuned Halloysite Nanotubes as Efficient and Recyclable Spongelike Adsorbents for Anionic Azo Dye Removal

The quest for sustainable development and green chemistry had led to the design and synthesis of advanced adsorbent materials for efficient removal of pollutants in industrial effluents. Magnetic halloysite nanotubes with chitosan nanocomposite sponges were prepared by combining solution-mixing and freeze-drying. Magnetic@chitosan/halloysite (Fe₃O₄-HNT/CS) and spongelike chitosan/halloysite (HNT/CS) were used as adsorbents for the removal of Congo red dye in aqueous solution in a batch process. The as-prepared composites were characterized using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, vibrating-sample magnetometry, thermal gravimetry-differential scanning calorimetry, and Fourier transform infrared spectroscopy. Data from kinetic study were analyzed with pseudo-first-order and pseudo-second-order models, whereas the mechanism was analyzed using Bangham's, Elovich's, intraparticle, and double-exponential diffusion models. The equilibrium data were evaluated using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The adsorption kinetics of dye removal followed the pseudo-first-order model with average rate constants of 0.260 and 0.196 min^-1 for Fe₃O₄-HNT/CS and HNT/CS, respectively. The Langmuir adsorption isotherm best fitted the equilibrium data with R ² > 0.9 with maximum adsorption capacities of 41.54 and 54.49 mg g^-1 obtained for HNT/CS and Fe₃O₄-HNT/CS, respectively. Negative values of ΔG° obtained from thermodynamic studies revealed that the adsorption process was spontaneous. The values of ΔH° and ΔS° obtained for Congo red dye removal were 69.46 and 39.54 kJ mol^-1 and 240.5 and 145.1 J mol^-1 K^-1 for HNT/CS and Fe₃O₄-HNT/CS, respectively. The results indicated that CS-HNT is an excellent adsorbent; however, its magnetic modification further improved its recyclability and enhanced the performance for the removal of Congo red dye from aqueous solution.

Kinetic, isotherm, and thermodynamic studies of the adsorption of dyes from aqueous solution by cellulose-based adsorbents

In this study, a highly efficient and eco-friendly porous cellulose-based aerogel was synthesized by grafting polyethyleneimine onto quaternized cellulose (PQC) to remove the anionic dye Congo Red (CR). The prepared aerogel had a good flexibility and formability. The adsorbents were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and elemental analysis. The results showed that there were many amino groups on CE/PQC aerogel and the structure was porous, which increased the adsorption capacity. The effects of initial concentration, adsorbent dose, contact time, temperature, and pH on the dye sorption were all investigated. The adsorption mechanism was also explored, including adsorption kinetics, adsorption isotherms and thermodynamic studies of adsorption. The results showed that the adsorption kinetics and isotherms fitted the pseudo-second-order kinetic model and Langmuir isotherm, respectively. The Langmuir isotherm revealed that the maximum theoretical adsorption capacity of the aerogels for CR was 518.403 mg g^-1. The thermodynamic parameters including Gibbs free energy change (ΔG⁰), enthalpy change (ΔH⁰) and entropy change (ΔS⁰), showed the adsorption process was exothermic and spontaneous. These results imply that this new absorbent can be universally and effectively used for the removal of dyes from industrial textile wastewater.

One step effective removal of Congo Red in chitosan nanoparticles by encapsulation

Chitosan nanoparticles (CNPs) were prepared with ionotropic gelation between chitosan and tripolyphosphate for the removal of Congo Red. The production of chitosan nanoparticles and the dye removal process was carried out in one-step. The removal efficiency of Congo Red by encapsulation within chitosan from the aqueous solution and its storage stability are examined at different pH values. The influence of some parameters such as the initial dye concentration, pH value of the dye solution, electrolyte concentration, tripolyphosphate concentration, mixing time and speed on the encapsulation is examined. Congo Red removal efficiency and encapsulation capacity of chitosan nanoparticles were determined as above 98% and 5107mg Congo Red/g chitosan, respectively.

Synthesis of magnetic graphene oxide-containing nanocomposite hydrogels for adsorption of crystal violet from aqueous solution

Magnetic nanocomposite hydrogels containing different amounts of graphene oxide were synthesized and characterized by FTIR, XRD, TGA, SEM, TEM, VSM and UV-vis spectroscopy.