Removing residual chlorine in water using carbon-based material derived from co-pyrolysis of cotton stalk and desulfurized ash

Herein, an environmentally friendly and low-caste absorbent has been studied to perform with high efficiency and fast removal rate of residual chlorine from wastewater. The chlorine removal absorbent was prepared in situ by co-pyrolysis of desulfurization ash (DA) and cotton stalk (CS) in a tube furnace at 600℃. Compared with CS pyrolysis alone, DA promoted the CS decomposition during co-pyrolysis of DA/CS. The maximum yield of pyrolysis gas was 188 mL/g with 11.33 MJ/Nm3, occurred in the DA/CS blending ratio of 50/100. Moreover, DA also catalyzed the well-developed micropore and mesoporous of cotton-stalk base carbon loaded with DA (CBCDA). The CBCDA with 38.62 wt% DA content had a pore volume of 0.0165 m3/g and a maximum specific surface area of 6.890 m²/g, which 1.96-fold and 1.50-fold higher than that of cotton-stalk base carbon, respectively. The further analysis of adsorption revealed that CaSO3 scattered on the surface of CBCDA fast and efficiently converted hypochlorite ion into chloride ion. The absorbent purified 90.02% residual chlorine from 12 mg/L wastewater within 30 min. Therefore, CBCDA absorbent offers a promising approach for fast and highly efficient purification of residual chlorine in wastewater.