Bio-based composite from chitosan waste and clay for effective removal of Congo red dye from contaminated water: Experimental studies and theoretical insights.

Water pollution due to dyes in the textile industry is a serious environmental problem. During the finishing stage, Congo red (CR) dye, water-soluble, is released into wastewater, polluting the water body. This study explores the effectiveness of utilizing a composite composed of Safi raw clay and chitosan to remove an anionic dye from synthetic wastewater. The chitosan was extracted from crab shells. Its removal performance was compared to that of natural clay. Both the composite and raw clay were used to remove target pollutant. The effects of the chitosan load in the composite, size particles, initial dye concentration, contact time, pH, and temperature on the dye's elimination were tested in batch modes. The composite with 30% (w/w) of chitosan exhibited the highest dye removal. At pH 2, an adsorption capacity of 84.74 mg/g was achieved, indicating that the grafting of the polymer onto clay surface enhances its efficacity and stability in acidic environments. This finding was supported by characterization data obtained from X-ray diffraction (XRD), scanning electron microscopy (SEM), dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FT-IR) analyses. Under optimized conditions of 20 mg dose, pH 2, 30 min of reaction time, and 20 mg/L of dye concentration, about 92% of dye removal was achieved. The Langmuir isotherm model represents dye adsorption by the composite, while dye removal was controlled by pseudo-second-order model. Thermodynamic data of the adsorption (ΔH = +8.82 kJ/mol; ΔG <0) suggested that the dye adsorption was spontaneous and endothermic. The findings provide insights into the dye elimination by the adsorbent, indicating that the removal occurred via attractive colombic forces, as confirmed by density functional theory (DFT) analysis. Overall, the composite of natural clays and chitosan waste is a promising and innovative adsorbent for treating wastewater containing recalcitrant dyes.

Fixed-bed adsorption of pesticide agricultural waste using cross-linked adsorptive hydrogel composite beads.

Adsorption column blockage due to solid adsorbent material is prevalent in laboratory-scale applications. Creating composite materials with stable geometries offers a viable solution. By crafting hydrogel beads using sodium alginate (Alg) and a bio-source like activated carbon (RMCA-P), it becomes possible to effectively eliminate agricultural pollutants, including the pesticide 2,4-D, from aqueous solutions. To evaluate the performance of these beads, a range of structural and textural analyses such as DRX, FTIR, SEM/EDX, BET, Zeta potential, Boehm titration, and iodine number were employed. Moreover, the study found that optimizing certain parameters greatly enhanced adsorption column efficiency. Specifically, increasing the bed height while reducing the flow rate of the adsorbate and the initial concentration in the inlet proved beneficial. The column demonstrated peak performance at a flow rate of 0.5 mL/min, a bed height of 35 cm, and an inlet adsorbate concentration of 50 mg/L. Under these conditions, the highest recorded removal rate for 2,4-D was 95.49%, which was subsequently confirmed experimentally at 95.05%. Both the Thomas and Yoon-Nelson models exhibited a good fit with the breakthrough curves. After undergoing three cycles of reuse, the RMCA-P/Alg hydrogel composite maintained a 2,4-D removal percentage of 74.21%. Notably, the RMCA-P/Alg beads exhibited effective removal of 2,4-D from herbicidal field waters in a continuous operational mode.

Eco-friendly synthesis of clay-chitosan composite for efficient removal of alizarin red S dye from wastewater: A comprehensive experimental and theoretical investigation.

Alizarin Red S (ARS) is commonly utilized for dyeing in textile industry. The dye represents a refractory pollutant in the aquatic environment unless properly treated. To tackle this pollutant, the applicability of chitosan-clay composite (3C) for the ARS removal from textile wastewater was studied. Characterization studies were conducted on the synthesized adsorbent using Fourier transformation infrared (FT-IR), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) techniques. Optimized parameters such as adsorbent's dosage, pH, reaction time, and initial concentrations were tested in a batch system. Additionally, density functional theory (DFT) was calculated to understand the adsorption mechanism and the role of benzene rings and oxygen atoms in the ARS as electron donors. At the same initial concentration of 30 mg/L and optimized conditions of 50 mg of dose, pH 2, and 10 min of reaction time, about 86% of ARS removal was achieved using the composite. The pseudo-second-order kinetic was applicable to model a reasonable fitness of the adsorption reaction, while the Temkin model was representative to simulate the reaction with a maximum adsorption capacity of 44.39 mg/g. This result was higher than magnetic chitosan (40.12 mg/g), or pure chitosan (42.48 mg/g). With ΔH = 27.22 kJ/mol and ΔG<0, the data implied the endothermic and spontaneous nature of the adsorption process. Overall, this implies that the clay-chitosan composite is promising to remove target dye from contaminated wastewater.