Removal of an Azo Dye from Wastewater through the Use of Two Technologies: Magnetic Cyclodextrin Polymers and Pulsed Light

Abstract

Water pollution by dyes is a huge environmental problem; there is a necessity to produce new decolorization methods that are effective, cost-attractive, and acceptable in industrial use. Magnetic cyclodextrin polymers offer the advantage of easy separation from the dye solution. In this work, the β-CD-EPI-magnetic (β-cyclodextrin-epichlorohydrin) polymer was synthesized, characterized, and tested for removal of the azo dye Direct Red 83:1 from water, and the fraction of non-adsorbed dye was degraded by an advanced oxidation process. The polymer was characterized in terms of the particle size distribution and surface morphology (FE-SEM), elemental analysis (EA), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), infrared spectrophotometry (IR), and X-ray powder diffraction (XRD). The reported results hint that 0.5 g and pH 5.0 were the best conditions to carry out both kinetic and isotherm models. A 30 min contact time was needed to reach equilibrium with a qmax of 32.0 mg/g. The results indicated that the pseudo-second-order and intraparticle diffusion models were involved in the assembly of Direct Red 83:1 onto the magnetic adsorbent. Regarding the isotherms discussed, the Freundlich model correctly reproduced the experimental data so that adsorption was confirmed to take place onto heterogeneous surfaces. The calculation of the thermodynamic parameters further demonstrates the spontaneous character of the adsorption phenomena (ΔG° = −27,556.9 J/mol) and endothermic phenomena (ΔH° = 8757.1 J/mol) at 25 °C. Furthermore, a good reusability of the polymer was evidenced after six cycles of regeneration, with a negligible decline in the adsorption extent (10%) regarding its initial capacity. Finally, the residual dye in solution after treatment with magnetic adsorbents was degraded by using an advanced oxidation process (AOP) with pulsed light and hydrogen peroxide (343 mg/L); >90% of the dye was degraded after receiving a fluence of 118 J/cm2; the discoloration followed a pseudo first-order kinetics where the degradation rate was 0.0196 cm2/J. The newly synthesized β-CD-EPI-magnetic polymer exhibited good adsorption properties and separability from water which, when complemented with a pulsed light-AOP, may offer a good alternative to remove dyes such as Direct Red 83:1 from water. It allows for the reuse of both the polymer and the dye in the dyeing process.

Metal Oxide Hydrogel Composites for Remediation of Dye-Contaminated Wastewater: Principal Component Analysis

“…Synthetic and organic dyes are mainly produced through the textile dyeing process. Azo dyes, which correspond to more than half of the total global production of dyes, represent a major part of artificial dyes [ 4 , 5 ]. Due to their complex molecular structure, synthetic dyes are known to be refractory to temperature [ 6 ], and very stable; hence, they are not easily biodegradable [ 7 ].…”

Cow Dung-Based Biochar Materials Prepared via Mixed Base and Its Application in the Removal of Organic Pollutants

“…The adsorption kinetics describes the change of adsorbent with contact time, and is often used to study the influence of adsorbate concentration and the control mechanism of chemical reactions in the adsorption process [ 36 , 37 , 38 ]. The consequences of contact time on removal of RhB and TH (100, 200, and 300 mg L −1 ) were shown as Figure 6 A–C and Figure 6 D–F by BMCD-K, BMCD-Na, and BMCD-MB.…”

“…The correlation coefficients ( R 2 ) of the Pseudo-first-order kinetic were 0.9764–0.9930, 0.9523–0.9876, and 0.9559–0.9784 for BMCD-K, BMCD-K, and BMCD-MB while the adsorbate was RhB, 0.9703–0.9892, 0.9883–0.9907, and 0.9859–0.9913 while the adsorbate was TH, meanwhile, all the theoretical Q e.cat calculated according to the Pseudo-first-order kinetic model were lower than the Q e obtained from the experiments, which indicates that the Lagergren’s model probably did not play a significant role during the adsorption process [ 36 ]. While the adsorption data of RhB and TH were fitted to the Intra-particle diffusion model, the correlation coefficients ( R 2 ) were 0.8205–0.9010 and 0.7407–0.8794 for BMCD-K, 0.7264–0.9135 and 0.7349–0.7626 for BMCD-Na, and 0.8164–0.9148 and 0.7467–0.8061 for BMCD-MB, meant that the Weber-Morris’s model was not able to explain this adsorption process [ 37 ]. The Pseudo-second-order kinetic model was fitted to the adsorption data of BMCD-K, BMCD-NA, and BMCD-MB, and the correlation coefficients ( R 2 ) were 0.9956–0.9988, 0.9963–0.9998, and 0.9904-0.9971 for RhB, and 0.9935–0.9998, 0.9990–0.9998, and 0.9989–0.9998 for TH, respectively.…”

Magnetic Luffa-Leaf-Derived Hierarchical Porous Biochar for Efficient Removal of Rhodamine B and Tetracycline Hydrochloride

“…The effect of concentration on adsorption capacity of adsorbent has usually been studied by studying adsorption isotherms [ 44 , 45 ]. The adsorption behaviors of adsorbents (LLB-MB and LLB-MB@Fe 3 O 4 ) and adsorbates (RhB and TH) at 303 K were investigated with different initial solution concentrations, and the results are shown in Figure 8 .…”

“…Meanwhile, the intensity factors ( n F ) of LLB-MBand LLB-MB@Fe 3 O 4 were 6.30 and 9.13 for RhB, and 3.27 and 4.01 for TH, respectively. In conclusion, it can be inferred that the adsorption processes of RhB and TH were not simple single-layer adsorption processes but were likely to accumulate in heterogeneous multilayer adsorption [ 44 , 45 , 46 ].…”