Influence of Environmental Factors on Hexavalent Chromium Removal From Aqueous Solutions by Nano‐Adsorbent Composites: Fid-Bau Portal

Influence of Environmental Factors on Hexavalent Chromium Removal From Aqueous Solutions by Nano‐Adsorbent Composites

Xue, Xiaoqin / Lv, Xiaoshu / Jiang, Guangming / Baig, Shams Ali / Xu, Xinhua

This study investigates the removal of Cr(VI) by nanoscale zero‐valent iron (nZVI)‐multiwalled carbon nanotubes (MWCNTs) composites from aqueous solutions. Various influential environmental factors including temperature, pH, co‐existing ions, and natural organic matters (NOM) on Cr(VI) removal were evaluated. Results revealed that temperature variations significantly influenced Cr(VI) removal and the efficiency decreased to 22% with increasing in temperature from 10 to 40°C. Cr(VI) removal efficiency decreased with increasing pH and the final pH increased to 9.1, 10.1, and 10.2 from 5, 7, and 9, respectively, after 2 h of the reaction. Interestingly, most of the co‐existing ions except copper presented comparatively lower final removal rates. However, co‐existing ions including Pd²⁺, Ca²⁺, Zn²⁺, and Mg²⁺ facilitated higher Cr(VI) removal. Copper was observed to greatly promote the reaction and 99.5% removal efficiency was achieved within 30 min after adding 20 mg L⁻¹ of Cu²⁺. In contrast, Cr(VI) removal efficiency drastically dropped to 58.9% from 97.9% in the presence of As(V). At higher concentrations of humic and tannic acid; the two representatives of NOM were observed to exhibit a negative impact on Cr(VI) removal. The changes appeared on nZVI‐MWCNTs before and after the reaction with Cr(VI) were investigated by transmission electron microscopy. The reusability of nZVI‐MWCNTs showed a recovery rate of 53.4% in the third round and demonstrated a better utility of nZVI‐MWCNTs composites in wastewater treatment applications.