THE PRETREATMENT OF ACRYLONITRILE AND STYRENE WITH THE OZONATION PROCESS

Acrylonitrile and styrene are used as the raw materials for manufactur ing acrylic fiber, thus they are often found as pollutants in the petr ochemical wastewater. This study utilizes ozone to decompose the organ ic nitrogen contained in acrylonitrile and styrene, and the oxidation process was monitored using on-line measurements of oxidation-reductio n potential (ORP) and pH. The efficiency of organic nitrogen decomposi tion was also estimated based on the GOD, organic nitrogen, TOC, ammon ia-N, nitrite, and nitrate measurements. Both the initial pH and alkal inity are observed to affect the degradation rate of organic nitrogen. The acrylonitrile sample with the lowest initial pH value (i.e., 4.0) has a shorter t(1/2) Of 18.9 min and that for samples of the highest initial pH (i.e., 11) was 34 min. The alkalinity of one acrylonitrile sample was boosted by adding 500 mg/l CaCO3, to simulate the field ABS (Acrylonitrile-Butadiene-Styrene) wastewater effluent. It was observe d that within a short ozone contact time, the acrylonitrile sample spi ked with 500 mg/l CaCO3 had the highest COD decomposition rate of 0.41 1 min(-1), or 1.3 times more than that for samples Without addition of CaCO3. Results of the ozonation process can be fitted with a modified Nernst equation for the various pH conditions. Additionally, the ozon e treated synthetic ABS sample shows a faster COD removal rate in the subsequent biological process than those samples without ozone treatme nt. (C) 1997 IAWQ. Published by Elsevier Science Ltd.