Engineered cerium-based adsorption materials for simultaneous removal of Cr(VI) and phenol: co-adsorption behavior and removal mechanism

Ce@C exhibited superior Cr(VI) and phenol adsorption capacity. • Cr(VI) and phenol possessed a synergistic adsorption effect in binary-component. • Phenol indirectly promoted the Cr(VI) reduction by reducing Ce(IV) to Ce(III). • Oxidized phenol increased the content of oxygen-containing functional groups in Ce@C. • Ce(III) formed complexes with phenol to enhance the phenol and Cr(VI) adsorption. Cerium-based adsorbent has unique advantages of variable valence and abundant oxygen vacancies for the adsorption of hexavalent chromium (Cr(VI)). However, complex water bodies contain organic pollutants such as phenol, and the adsorption performance and mechanism of cerium-based adsorbent for multiple components still need to be explored. Herein, cerium-based adsorbent (Ce@C) was synthesized to explore the single-component and binary-component adsorption properties of Cr(VI) and phenol. Compared with single-component adsorption, Ce@C exhibited excellent adsorption performance for Cr(VI) and phenol in multi-component, with maximum adsorption capacities reaching 55.74 and 89.34 mg/g respectively at 25 °C (C e(Cr(VI))  = 50 mg/L, C e(phenol)  = 150 mg/L). Ce@C showed excellent regeneration performance, and Cr(VI) adsorption capacity remaining almost stable and phenol adsorption capacity increasing by 30.44% after 5 cycles. The adsorption capacities of Cr(VI) and phenol were 1.78 times and 1.42 times higher than that of the single-component system, respectively, demonstrating a significant synergistic enhancement effect. Mechanistic results indicated that phenol transferred electrons to Cr(VI) through Ce(III), facilitating the reduction of Cr(VI) to Cr(III) and increasing the content of oxygen-containing functional groups. The complex formed by Cr(III) and phenol enhanced the phenol adsorption, enabling the continuous adsorption of Cr(VI) and phenol. This study provides new insights into improving the removal performance of Ce-based adsorbents for Cr(VI) and phenol in composite systems, further expanding the application potential of Ce-based adsorbents in the treatment of actual wastewater containing Cr(VI) and phenol. Download: Download high-res image (172KB) Download: Download full-size image