Complex extraction and stripping of H acid wastewater

H acid is an important dye intermediate for the synthesis of direct, reactive and azo dyes. In this study, the method of complex extraction and stripping has been introduced for the treatment of high concentrated H acid wastewater. The extractant and diluent selected in the experiment are trialkylamine (N7301) and kerosene, respectively. And the dependencies of the extraction efficiency on the extractant concentration, the initial pH value, the volume ratio of water to oil (W/O), and the temperature are investigated. Under the optimum condition that kerosene/N7301 of 3:1, pH of 1.0, W/O of 2:1, and temperature of 45°C, through three-stage extraction, the CODcr value of H acid wastewater decreases from 13828.48 mg/l to 199.21 mg/l, and the overall CODcr removal rate can reach 98.56%. Finally, the extractant can be regenerated by stripping process with 10% NaOH, and the stripping rate can arrive at 100%. Compared with other methods, complex extraction and stripping is considered as a much more efficient and feasible one not only for that the extractant regenerated can reduce the operation cost but also for that the H acid extracted can be reused in the production process without degradation, which meets the requirement of zerodischarge and no sludge.