Removal of Cr(VI) by modified and immobilized Auricularia auricula spent substrate in a fixed-bed column

Abstract

To remove the heavy metals from industrial wastewater and reclaim valuable materials from edible fungus production, Auricularia auricula spent substrate (AASS) modified by cetyltrimethyl ammonium bromide (CTAB) and immobilized by sodium alginate was used as a novel adsorbent (MIAASS) for Cr(VI) removal. The modification and immobilization did not change the surface morphology, but changed the property of the adsorbents revealed by SEM, BET and FT-IR analysis. Batch adsorption experiments showed the modification and immobilization had the uptake capacity improved 21.44 to 27.34% at influent Cr(VI) concentration ranging from 25 to 125mg/L. In fixed-bed column adsorption experiments, the breakthrough and exhaustion time were prolonged about 2 to 4.5 times with bed height increasing from 50 to 70cm, influent concentration and flow rate decreasing from 200 to 50mg/L and 40 to 20mL/min respectively. The concentration-time profile and the adsorption process was better predicted and described by Thomas model than Adams-Bohart model indicating that the external and internal diffusions were not the bottle neck of the process. The stability of MIAASS was validated through three cycles of adsorption-desorption processes, and the final regeneration efficiency amounted to 52.48%.