Effective removal of anionic textile dyes using adsorbent synthesized from coffee waste

Enhanced Removal of Soluble and Insoluble Dyes over Hierarchical Zeolites: Effect of Synthesis Condition

A hierarchical zeolite ZSM-5 with micro and meso-pore was prepared by optimising the most affecting parameter in sequence of desilication and dealumination. The physicochemical properties of zeolite were characterised with XRD, nitrogen adsorption–desorption, FTIR and SEM. The potential of this zeolite for decolorisation of CR, RY, MB, RhB, DB-1 and DB-14 was evaluated with adsorption isotherm, thermodynamics, kinetics, and influencing parameter for adsorption. The unique modification of ZSM-5 resulted in lower crystallinity, easier porosity control, rich terminal silanol and unbridged silanol groups which assisted in higher adsorption capacity. The adsorption capacity of the optimum ZSM-5 was 323, 435, 589, 625, 61 and 244 mg/g for CR, RY, MB, RhB, DB-1 and DB-14, respectively. The dye adsorption progressed through pseudo-first-order kinetic and close to the Langmuir model. The adsorption mechanism is proposed mainly through interaction between deprotonated silanol site and the electron-rich dye site.

Synthesis, characterization, and regeneration of an inorganic-organic nanocomposite (ZnO@biomass) and its application in the capture of cationic dye

Despite the efficiency of ZnO nanoparticle (NPs) composite adsorbents in the adsorption of various pollutants, there is presently no report on the combo of ZnONPs with biomass for adsorption. Besides, there is a dearth of information on the biosorption of celestine blue (CEB), a dye used in the nuclear and textile industry. In this study, biogenic-chemically mediated synthesis of a composite (ZnO@ACP) was prepared by the impregnation of ZnONPs onto Ananas comosus waste (ACP) for the adsorption of CEB. The SEM, EDX, FTIR, XRD, BET, and TGA characterizations showed the successful presence of ZnONPs on the biomass to form a nanocomposite. The uptake of CEB was enhanced by the incorporation of ZnONPs on ACP. A faster CEB adsorption onto ZnO@ACP (120 min) compared to ACP (160 min) was observed. The Langmuir (R² > 0.9898) and pseudo-second-order (R² > 0.9518) models were most appropriate in the description of the adsorption process. The impregnation of ZnONPs onto the biomass enhanced the spontaneity of the process and displayed endothermic characteristics. High CEB desorption of 81.3% from the dye loaded ZnO@ACP as well as efficient reusability showed the efficacy of the prepared nanocomposite for CEB adsorption.

Effective Adsorption of Reactive Black 5 onto Hybrid Hexadecylamine Impregnated Chitosan-Powdered Activated Carbon Beads

In this study, hexadecylamine (HDA) impregnated chitosan-powder activated carbon (Ct-PAC) composite beads were successfully prepared and applied to adsorption of the anionic dye reactive black 5 (RB5) in aqueous solution. The Ct-PAC-HDA beads synthesized with 0.2 g powdered activated carbon (PAC) and 0.04 g HDA showed the highest dye removal efficiency. The prepared beads were characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Various adsorption parameters, i.e., adsorbent dosage, pH, and contact time, which affect the adsorption performance, were studied in a series of batch experiments. The obtained adsorption data were found to be better represented by Freundlich (R2 = 0.994) and pseudo-second-order (R2 = 0.994) models. Moreover, it was ascertained that the adsorption of RB5 onto Ct-PAC-HDA beads is pH-dependent, and the maximum Langmuir adsorption capacity (666.97 mg/g) was observed at pH 4. It was also proved that Ct-PAC-HDA beads were regenerable for repeated use in the adsorption process.

Exfoliated Clay Decorated with Magnetic Iron Nanoparticles for Crystal Violet Adsorption: Modeling and Physicochemical Interpretation

Surfactant–modified exfoliated Fayum clay (CTAB–EC) obtained after chemical treatment with a CTAB/H₂O₂ solution was further decorated with magnetic Fe₃O₄ nanoparticles (MNP). The final nanocomposite (MNP/CTAB–EC) was characterized by XRD, SEM, FTIR, TEM and its adsorptive capability against a model cationic dye, crystal violet (CV), was evaluated. A comparison of the adsorption performance of the raw clay and its modified counterparts using H₂O₂, CTAB, CTAB/H₂O₂ or MNP indicated that the adsorption capacity of MNP/CTAB–EC was the highest for CV removal at pH 8.0. The pseudo‒second order for the kinetics and Freundlich model for adsorption equilibrium fitted well the CV removal experimental data at all tested temperatures (25, 40 and 55 °C). The enhancement of the Langmuir adsorption capacity from 447.1 to 499.4 mg g⁻¹ with increasing the temperature from 25 to 55 °C revealed an endothermic nature of the removal process. The interactions between CV and MNP/CTAB–EC were interpreted using advanced statistical physics models (ASPM) in order to elucidate the adsorption mechanism. Multilayer model fitted the adsorption process and therefore, the steric and energetic factors that impacted the CV adsorption were also interpreted using this model. The aggregated number of CV molecules per MNP/CTAB–EC active site (n) was more than unity at all temperatures, representing thus a vertical adsorption orientation and a multi‒interactions mechanism. It was determined that the increase of CV uptake with temperature was mainly controlled by the increase of the number of active sites (N_M). Calculated adsorption energies (ΔE) revealed that CV removal was an endothermic and a physisorption process (ΔE < 40 kJ mol ⁻¹). MNP/CTAB–EC was magnetically separated, regenerated by NaOH, and reused without significant decrease in its adsorption efficiency, supporting a prosperity of its utilization as an effective adsorbent against hazardous dyes from wastewaters.

Cereus sp. as potential biosorbent for removal of Congo red from aqueous solution: isotherm and kinetic investigations

Elimination of toxic dyes from industrial effluents before discharge into the environment is very essential to reduce the impact created on the environment. The process of adsorption is widely used for the removal of toxic dyes through suitable adsorbents. In the present study, a novel adsorbent prepared from Cereus sp. for the removal of Congo red from the aqueous solution phase. Adsorption experiment was conducted in batch mode and the effect of adsorbent dose (1-12 g/l), dye concentration (100-250 mg/l), and contact time (5-120 min) was determined. Twelve isotherm models namely Langmuir, Freundlich, Jovanovic, Temkin, Elovich, Dubinin-Radushkevich, Halsey, Hill-Deboer, Flory-Huggins, Flower-Guggenheim, Kiselev, and Harkins-Jura were fitted with the experimental data. Cuticle-removed cladodes (CRC) from biomass gave maximum adsorption capacity of 27.02 mg/g, whereas cuticle (C) resulted in maximum adsorption capacity of 52.63 mg/g according to Langmuir isotherm. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion kinetic models were examined. Pseudo-second-order kinetics better fitted for both adsorbents. This is the first exhaustive study to systematically find cuticle portion has better adsorption of Congo red than the cladodes of Cereus sp. The study also highlights that cutin polyesters present in the cuticle might be responsible for higher adsorption of dyes compared with its counterpart CRC. The present study provides the first evidence that cutin polymer can be used for adsorption of Congo red. It significantly contributes to advancement for new biobased materials for monitoring and remediation of water resources contaminated with toxic dyes.