| Summary: | 碩士 === 元智大學 === 化學工程學系 === 91 === Abstract
Phenolic compounds are commonly present in various industrial wastewaters. Coal mining, petrochemical refining and coal tar making are typical industries where phenolic compounds exist in the wastewater. Currently, popular methods employed by the industries for treating phenolic wastewater include biological treatment, liquid extraction, adsorption using macroreticular resins and chemical oxidation. Although effective, these methods can only handle phenolic wastewater of limited concentration. Unfortunately, in many cases, the petrochemical wastewater can have phenol concentration exceeding 10,000 mg/l. The treatment method noted above become inadequate . Hence development of chemical or physical methods that is capable of handing high-concentration is necessary. In the present study, we developed a chemical precipitation method in conjunction with adsorption by macroreticular resins for tackling wastewaters containing m-methyl phenol, p-benylphenol or chlorphenol.
Chemical precipitation is to utilize a metal chloride or similar chemicals to react with phenolic compound in the wastewater under alkaline conditions. Due to its low solubility in water, the metal phenolate precipitates out, simultaneously lowering the phenolic concentration in the wastewater. Batch experiments were conducted to explore the effects of pH, amount of metal chloride and temperature on the chemical reaction and phenolate precipitation. Test results indicate that an increase in initial wastewater pH significantly enhances the phenol removal. Ferrous and barium chlorides were found to yield the best overall results in terms of phenol removal and speed of phenolate precipitation. Stoichiometric amount of metal chloride or slightly more than this amount was found sufficient to effect good chemical precipitation.
The phenolic concentration of the wastewater after chemical precipitation was much reduced. Hence adsorption by macroreticular resin was adopted to remove the remaining phenolic compounds. Batch and column experiment tests using XAD-4 were performed to identify the optimum operating conditions. The batch test results show that the extended Langmuir could satisfactorily describes the solid/liquid equilibrium of phenolic compounds. The breakthrough data obtained from column tests reveal that the models of the simplified logistic, Richards or Hill type would be adequate to represent the observed breakthrough data. The phenolic concentration of the wastewater after adsorption was lower than the discharge standard.
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