Fixed-bed adsorption of copper from aqueous media using chitosan-coated bentonite, chitosan-coated sand, and chitosan-coated kaolinite.

Fixed-bed studies were performed to evaluate the removal efficiency of copper (Cu(II)) from aqueous solution using chitosan-coated bentonite (CCB), chitosan-coated sand (CCS), and chitosan-coated kaolinite (CCK). The thermal and morphological properties of CCB, CCK, and CCS were characterized using thermogravimetric analysis, Fourier transform infrared spectroscopy, and the Brunauer-Emmett-Teller method. Dynamic experiments were carried out to investigate the effect of solution pH (3.0 to 5.0) and initial Cu(II) concentration (200 to 1000 mg/L) on the time to reach breakthrough (tb), total volume of treated effluent (Veff), and adsorption capacity at breakthrough (qb). Results show that increasing the initial Cu(II) concentration inhibits the column performance where lower Veff, tb, and qb were obtained. Decreasing the pH from 5.0 to 3.0 led to improved removal efficiency with higher values of Veff, tb, and qb. Under pH 3.0 and 200 mg/L, the maximum removal efficiency of 68.60%, 56.10%, and 58.90% for Cu(II) was attained using CCB, CCS, and CCK, respectively. The Thomas model was determined to adequately predict the breakthrough curves based on high values of coefficient of determination (R2 ≥ 0.8503). Regeneration studies were carried out using 0.1 M HCl and 0.1 M NaOH solution in the saturated column of CCB, CCK, and CCS.

Treatment of soil washing wastewater via adsorption of lead and zinc using graphene oxide.

In the present work, graphene oxide (GO) was synthesized via the modified Hummers method and utilized in treating real soil washing wastewater via adsorptive removal of lead (Pb) and zinc (Zn). Characterization analysis of GO was performed using X-ray diffraction, Brunauer-Emmett-Teller method, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and zeta potential analysis. The Van't Hoff, Eyring, and Arrhenius equations were applied to determine the activation and thermodynamic parameters namely activation energy (Ea), standard Gibbs energy change (ΔG°), standard enthalpy change (ΔH°), standard entropy change (ΔS°), change in activation Gibbs energy (ΔG#), change in activation enthalpy (ΔH#), and change in activation entropy (ΔS#). Based on the high coefficient of determination values (0.8882 ≥ R2 ≥ 0.9094) and low values of SSE (0.0292 ≤ SSE ≤ 0.0511) and ARE (0.8014 ≤ ARE ≤ 0.8822), equilibrium data agreed well with the Freundlich isotherm. The maximum adsorption capacity for Pb(II) and Zn(II) was determined to be 11.57 and 4.65 mg/g, respectively. Kinetic studies revealed that pseudo-second-order equation fitted well with the experimental data, which indicates that chemisorption is the rate-determining step of the adsorption system. Results have shown the possibility of GO as a potential adsorbent material in the treatment of soil washing wastewater.