Process optimization for treatment of methyltin mercaptide effluents using modified semi-coke

WANG Xin(王欣)^1,2,3, C. Srinivasakannan³, QU Wen-wen(曲雯雯)^1,2, PENG Jin-hui(彭金辉)^1,2, ZHANG Li-Bo(张利波)^1,2, DUAN Xin-hui(段昕辉)^1,2, LU Shuai-dan(卢帅丹)^1,2

(1. Key Laboratory of Unconventional Metallurgy of Ministry of Education
(Faculty of Metallurgy and Energy Engineering, Kunming University of Science and Technology),
Kunming 650093, China;
2. Engineering Laboratory of Microwave Application and Equipment Technology, Kunming 650093, China;
3. Chemical Engineering Program, The Petroleum Institute, P.O. Box 2533, Abu Dhabi, UAE)

Abstract:The central composite process optimization was performed by response surface methodology technique using a design for the treatment of methyltin mercaptide with modified semi-coke. The semi-coke from the coal industry was suitably modified by treating it with phosphoric acid, with a thermal activation process. The objective of the process optimization is to reduce the chemical oxygen demand (COD) and —N in the methyltin mercaptide industrial effluent. The process variables considered for process optimization are the semi-coke dosage, adsorption time and effluent pH. The optimized process conditions are identified to be a semi-coke dosage of 80 g/L, adsorption time of 90 min and a pH value of 8.34. The ANOVA results indicate that the adsorbent dosage and pH are the significant parameters, while the adsorption time is insignificant, possibly owing to the large range of adsorption time chosen. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy and nitrogen adsorption isotherm. The average BET surface area of modified semi-coke is estimated to be 915 m²/g, with the average pore volume of 0.71 cm³/g and a average pore diameter of 3.09 nm, with micropore volume contributing to 52.36%.

Key words:modified semi-coke; semi-coke; optimization; water treatment; chemical oxygen demand (COD); —N