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The purpose of this research was to synthesise the chitosan-polyacrylamide composite (CH-PAA) and follow up with an investigation of its capacity to adsorb anionic Sirius yellow K-CF dye, under different environmental conditions. In order to increase the uptake value of the synthesised CH-PAA, the surface chemistry of this adsorbent was modified by bringing it into contact with ZnO nanoparticles (CH-PAA-ZnO). The characterisation tests using XRD, FT-IR, TEM, and FE-SEM analyses demonstrated the successful loading of ZnO onto the CH-PAA surface without causing damage to the chemical composition of the original materials. Excellent removal efficiency of the Sirius yellow K-CF dye (≈ 100%) by CH-PAA-ZnO was performed under the conditions cited namely, pH of 2, dye concentration of20 mg/L, adsorbent dosage of 0.05 g/L, temperature of 40°C, and contact time of 90 minutes. It was evident that the ZnO nanoparticles strongly facilitate the removal process, in which 42% enhancement of dye removal efficiency was recorded, after the CH-PAA was modified with these nanoparticles. The values of the thermodynamic parameters determined at different concentrations of Sirius yellow K-CF dye (negative $$\Delta {{\rm{G}}^{\rm{o}}}$$ Δ G o values; and positive $$\Delta {{\rm{H}}^{\rm{o}}}$$ Δ H o and $$\Delta {{\rm{S}}^{\rm{o}}}$$ Δ S o values) indicated that the dye adsorption process onto the CH-PAA-ZnO was favourable, spontaneous, and endothermic. Based on the R2 values (> 0.99) of the linear fitting determined, the experimental data pertinent to the isotherm and kinetic studies are represented by the Langmuir isotherm and pseudo-second-order kinetic formulas, respectively. Also, the isotherm study revealed that 1 g of CH-PAA-ZnO was capable of capturing 149.79 mg of the dye molecules in 1 L aqueous solution. On comparison with the other adsorbent used for the same purpose, the CH-PAA-ZnO can be an efficacious adsorbent and a good alternative to treat wastewater containing Sirius yellow K-CF dye, in an acidic medium. [ABSTRACT FROM AUTHOR]

The present experimental study aimed to determine the efficiency of CuS-coated magnetic activated carbon nanocomposite for the photocatalytic removal of tetracycline (TC) under simulated sunlight. The effects of pH 3, 5, 7, 9, contaminant concentration 5-10-20-50-100 mg/L, nanocatalyst dose 0.025, 0.25, 0.5, 1, 1.5, 2, and 2.5 g/L, and exposure time 1-200 min on the TC removal by the synthesized nanocatalyst were investigated. The maximum removal efficiency was achieved at pH = 9. The TC removal efficiency increased with increasing exposure time and decreasing TC concentration from 100% to 52.1%. The TC removal ratio initially (increased with increasing the nanocatalyst dose from 0.025 to 1.5 g/L (from 37.52% to 89.13%) but started to decrease (54.43%) once the dose was raised above a certain level. The kinetics of the process was found to closely follow the pseudo-first-order kinetic model with R2 > 0.9. After determining the optimal conditions for TC removal with the synthesized nanocatalyst under simulated sunlight, the chemical oxygen demand (COD) and total organic carbon (TOC) removal rates under the same conditions were also experimentally investigated. This investigation showed the COD and TOC removal rates to be 78.13% and 65.81%, respectively. The test results also showed the high recoverability and reusability of the synthesized nanocomposite, with only a 6.08% drop in removal efficiency after six cycles. Also, the effects of some scavenging agents were studied and the results showed the most important role of IPA as a hydroxyl radical scavenger in decreasing the photocatalytic activity of nanocomposite. This confirms that hydroxyl radicals play the most important role in the degradation of tetracycline molecules with respect to e-/h+ pairs or •O2-. Overall, the results demonstrated the excellent tetracycline removal capability of the synthesized nanocomposite under simulated sunlight. [ABSTRACT FROM AUTHOR]

In this study, we investigated the influence of a novel magnetic activated carbon (MAC) nanocomposite coated with CuS (MAC/CuS) on the successful removal of tetracycline (TC) molecules from aqueous solutions via adsorption. The physical and structural properties of the synthesized sorbent were determined using the field-emission scanning electron microscopy, Brunauer–Emmett–Teller, X-ray diffraction, Fourier-transform infrared spectroscopy, and vibrating-sample magnetometer techniques. Equilibrium isotherms and adsorption kinetics were studied. Additionally, the effects of pH (3, 5, 7, and 9), TC concentration (5–100 mg/L), MAC/CuS dosage (0.025–2.5 g), temperature (5°C, 10°C, 20°C, 40°C, and 50°C), and contact time (from inception to 200 min) were extensively examined. Our results revealed that the highest TC removal percentage was approximately 70% under optimal conditions (pH = 9, contact time = 200 min, nanocomposite dosage = 2 g/L, and temperature = 20°C). Modelling of the experimental data using isothermal models indicated that the TC adsorption process followed the Temkin model. Thermodynamic analyses revealed that the adsorption process was spontaneous and exothermic. A kinetic study demonstrated that the pseudo-second-order kinetic model was best for describing TC adsorption. This work presents a magnetic activated carbon nanocomposite coated with CuS as a high-efficiency adsorbent for the remediation of wastewater loaded with TC. [ABSTRACT FROM AUTHOR]