Phosphate removal from domestic wastewater using thermally modified steel slag
Jian Yu
,
Wenyan Liang
,
Li Wang
,
Feizhen Li
,
Yuanlong Zou
,
Haidong Wang
DOI:10.1016/j.jes.2014.12.007
Received July 16, 2014,Revised December 01, 2014, Accepted , Available online May 19, 2015
Volume 27,2015,Pages 81-88
This studywas performed to investigate the removal of phosphate fromdomesticwastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water, and thermal modification were investigated. The results showed that thermal activation at 800℃ for 1 hrwas the optimumoperation to improve the adsorption capacity. The adsorption process of the thermallymodified slagwas well described by the Elovich kineticmodel and the Langmuir isotherm model. The maximum adsorption capacity calculated from the Langmuir model reached 13.62 mg/g. Scanning electron microscopy indicated that the surface of the modified slag was cracked and that the texture became loose after heating. The surface area and pore volume did not change after thermal modification. In the treatment of domestic wastewater, the modified slag bed (35.5 kg) removed phosphate effectively and operated for 158 days until the effluent P rose above the limit concentration of 0.5 mg/L. The phosphate fractionation method, which is often applied in soil research, was used to analyze the phosphate adsorption behavior in the slag bed. The analysis revealed that the total contents of various Ca-P forms accounted for 81.4%-91.1%, i.e., Ca10-P 50.6%-65.1%, Ca8-P 17.8%-25.0%, and Ca2-P 4.66%-9.20%. The forms of Al-P, Fe-P, and O-P accounted for only 8.9%-18.6%. The formation of Ca10-P precipitates was considered to be the main mechanism of phosphate removal in the thermally modified slag bed.
