Study On Complexing Extraction Of Aromatic Sulfonic Acids

Aromatic sulfonic acids refer to aromatic compounds that have at least one sulfo group on the aromatic ring, other substituent groups may also exist on the ring, such as methyl, amino, hydroxy, carboxyl, halogen, nitro group, etc. These compounds occupy an important position in the chemical industry, especially in the dye industry; many of them or their alkali salts are important intermediates for the manufacture of dyes and pigments. Generally, these compounds can be divided into three kinds according to the aromatic ring, i.e., benzene series, naphthalene series and anthraquinone series. Production of the aromatic sulfonic acids meets the need of dye industry; however, it leads to serious environmental problems at the same time, especially the treatment of the wastewater discharged during the production process.In this thesis, complexing extraction of sulfanilic acid, p-toluenesulfonic acid, naphthalene-1,5-disulfonic acid and anthraquinone-2-sulfonic acid were studied. Such effects as complexing agent’s structure on its extraction ability, aromatic sulfonic acid’s structure on its ability to be extracted and diluent’s kind and dosage on extraction efficiency were investigated. Results show that tertiary amine with less steric hindrance and shorter carbon chain would have stronger extraction ability. However, as the carbon chain gets shorter, water solubility of tertiary amine itself and the ammonium salt it forms with the aromatic sulfonic acid would also increase. For a certain kind of aromatic sulfonic acids, whether it is easy to be extracted mainly depends on two factors, one is whether amino group exists on the aromatic ring, the other is the hydrophobicity of the aromatic ring. Using of polar diluents could achieve largger distribution coefficient, while polar diluents are not suitable for complexing extraction process when more factors are taken into consideration comprehensively, such as water solubility, safety, cost, etc. Sulfonated kerosene proves to be a good choice as diluent for complexing extraction process though it is nonpolar.With trioctylamine as complexing agent and sulfonated kerosene as diluent, extraction of CLT acid wastewater was studied. Effects of such factors on extraction efficiency as pH of wastewater, temperature, stirring speed, stirring time, settling time and phase ratio were investigated with the method of single factor experiment. The optimum parameters obtained were as follows:pH of wastewater1.10, temperature20℃, stirring speed400rpm, stirring time60min and settling time60min, phase ratio6. Under these conditions, COD of the raffinate was260mg·L-1after single stage extraction with the corresponding COD removal rate reaching99.28%, besides, the raffinate was clear and colorless in the appearance.At last, continuous extraction of CLT acid wastewater was studied in the rotating disc column and an integrated process for continuous extraction of CLT acid wastewater was proposed. Results show that cocurrent extraction could achieve good extraction efficiency; when volume flow rate ratio of wastewater to extractant was6, stirring speed was450rpm and residence time was60min, COD of the raffinate was288mg·L-1. Undoubtedly this would have very important guiding significance for continuous extraction of other aromatic sulfonic acids wastewater.