焦化废水缓冲体系的存在证明与集水调节池中水质结构调控

The buffer system in coking wastewater and the water quality control in water regulating tank

采用FeSO4对焦化废水原水进行pH调节,发现焦化废水原水中存在酸碱缓冲体系,具有很强的酸碱缓冲能力.焦化废水原水pH值约为9.6时,HCO3-、CN-、HS-、S2-、NH3、C6H5O-和胺类等以共轭碱的形式存在,对应的缓冲容量较高;随着pH的降低,共轭碱所占比例逐渐减少,对应的弱酸分布分数逐渐增多,缓冲容量逐渐减小;当pH调节至中性时,pH与pKa值接近,共轭碱与弱酸的分布分数近似相等,废水的缓冲容量有升高的趋势.在调节pH的过程中,由于FeSO4的水解、沉淀与络合作用,在投加量为2.0 g.L-1,反应时间15 min时,焦化废水中的氰化物、硫化物、油分及COD的去除量分别为1.5 mg CN-.g-1、27.3 mg S2-.g-1、15 mg总油.g-1及504 mg COD.g-1,pH影响各种污染物的形态分布而实现水质结构的调控.

Based on the chemical characteristics of coking wastewater,pH adjustment by ferrous sulfate was conducted and a strong acid-base buffering capacity was found in coking wastewater.At the original pH of 9.6,HCO-3,CN-,HS-,S2-,NH＋4,phenol and aniline existed as their conjugate base,which corresponded a high buffer capacity.With the reduction of the pH value,the ratio of the conjugate base decreased and the buffer capacity became smaller.At the pH of 7,the ratio of conjugate base and conjugate acid were approximately equal because pH was close to pKa and the buffer capacity had a growing tendency.Moreover,the hydrolysis of FeSO4 had a coagulating and complexing effect for pollutants.The removal amounts of CN-,S2-,oil and COD were 1.5,27.3,15,and 504 mg · g-1 with the FeSO4 dosage of 2.0 g · L-1 in 15 minutes.pH has an influence on the concentration distribution of various pollutants so that it is critical for controlling the structure of water quality.Therefore,it is expected that pH can be a useful parameten for controlling the quality of coking wastewater under the acid-base buffering system.