Journal of Hazardous, Toxic, and Radioactive Waste

The present work explores the adsorption potential of $\mathit{\gamma }$-alumina, a nanoadsorbent for abatement of Ni(II) from aqueous solutions. A response surface methodological approach was adopted to investigate the major operating variables and optimization of experimental conditions. The predicted values of responses obtained using the response function were in accordance with the experimental data. Under optimized conditions, removal of about 99.99% of Ni(II) was achieved. Langmuir isotherm and pseudo-second-order kinetics best interpreted the experimental data. The overall process was feasible, spontaneous, and endothermic in nature. The high correlation coefficient ($R^2$) values of the linear method of analysis established its superiority over a nonlinear method for the present system.

Arsenic-contaminated groundwater affects millions worldwide. A cement-based filter medium (CBFM) can be used to remediate heavy metals from groundwater. Recently, the desulfurization of flue gas in coal-fired power plants has increased sulfur content in fly ash, exceeding standard limits for use in normal concrete, thereby limiting beneficial reuse. This study investigated arsenic remediation by CBFM samples produced with high-sulfur fly ashes, waste synthetic gypsum, sodium sulfide, and elemental sulfur. Hardened concrete was batch tested in arsenic-contaminated deionized (DI) water and synthetic groundwater (SG) to elucidate ion competition. Arsenic removal exceeded 90% for all CBFM specimens in DI water, apart from sodium sulfide samples. In SG, elemental-sulfur and high-sulfur fly ash CBFM mixtures had 60%–85% removal at all tested concentrations. Scanning electron microscopy and X-ray diffraction spectroscopy showed a uniform distribution of arsenic, indicating high diffusivity throughout the cementitious paste. Arsenic removal occurred in two primary mechanisms: precipitation through the formation of calcium arsenate complexes and adsorption onto calcite, ettringite, and monosulfate. This research could lead to the use of CBFM as a readily available and waste valorizing remediation tool for arsenic-impacted areas.

This study evaluates the technoeconomic feasibility of using hybrid advanced oxidation technologies (AOTs) for the removal of chlortetracycline (CTC) in wastewater treatment plant (WWTP). Experimental results on wastewater (WW) and wastewater sludge (WWS) matrices were taken into consideration for the technoeconomic evaluation comprising five different AOT methods. Degradation efficiency of CTC removal varied according to the matrix (WW or WWS) and on the application of individual or hybrid AOPs. A balance between the technical aspect (treatment efficiency parameter) and economic constraints has been equally maintained while evaluating the removal of CTC using AOPs under both the matrix. Among AOTs, namely ultrasonication (UIS), Fenton oxidation (FO), and ferro-sonication (FS) used to treat CTC in WWS, FS was considered as the most feasible technoeconomic solution while ultrasonic assisted laccase (UAL) showed a better technoeconomical option when compared to the sulfate radical based degradation processes ($\mathrm{persulfate}/{\mathrm{Fe}}^{2+}/{\mathrm{Fe}}^0$) to remove CTC in WW.