苯甲酸生产废水的处理与资源化

为有效地回收甲苯液相氧化法生产苯甲酸的工业废水中的苯甲酸和乙酸,并配合废水生物降解的末端处理技术,研究了20%,30%和50%磷酸三丁酯(TBP)/煤油的混合溶剂、正辛醇和甲苯萃取苯甲酸稀溶液特性,以及对工业废水处理的实验.结果表明,TBP对苯甲酸稀溶液具有良好的萃取作用,而纯溶剂体系与溶剂的极性有关,正辛醇的萃取能力与30%TBP相当;残液中的COD_Cr值由萃取剂在水中的溶解和苯甲酸自身的COD_Cr值组成,其中残液中溶剂溶解导致的COD_Cr值随其中苯甲酸浓度变化不明显,且COD_Cr值的大小为:50%TBP≈30%TBP>正辛醇>20%TBP>甲苯.针对工业废水中主要含有苯甲酸和乙酸的工况,提出了废水资源化的处理工艺流程,即首先采用甲苯进行废水中苯甲酸的回收,之后,再利用三烷基氧磷/煤油为萃取剂回收废水中的醋酸,进一步生产绿色化学品乙酸钙镁盐.

Pretreatment and Resource Utilization of Industrial Effluent with Benzoic Acid

Extraction equilibrium of benzoic acid were studied using 20%, 30% and 50% tributyl phosphate (TBP) in kerosene, 1-octanol and toluene as the extractants, to investigate the efficient method of recovering benzoic and acetic acid in the industrial effluent and meeting the requirement of the terminal wastewater treatment. The CODCr value in residual phase and the recovery of benzoic acid in various extractants were measured. The results showed that the recovery of benzoic acid was closed to 100% with 50% TBP/kerosene system, and depended on the polarity of extractant for pure solvent system. The recovery with 1-octanol was equivalent to the one with 30% TBP. The CODCr value in the residual phase depended on the CODCr value from benzoic acid and the solubility of extractant, which does not depend on the benzoic acid concentration in the residue phase apparently, and shown 50% TBP approximately equal to 30% TBP > 1-octanol > 20% TBP > toluene. Meanwhile, the profitable diagram of pretreatment of industrial effluent with benzoic acid was suggested, i.e. firstly, extract benzoic acid with toluene and return the toluene to the benzoic acid reactor, then, extract acetic acid with trialkylphosphine oxide and back-extract the acetic acid with CaO or MgO to produce calcium magnesium acetate.