焦粉吸附深度处理焦化废水研究

为解决焦化废水经常规生化处理后污染指标不符合排放标准的问题,将焦化厂生产过程中自身产生的焦粉用于焦化厂废水处理工艺中生化出水的深度处理环节,考察了焦粉投加量、焦粉粒径、溶液pH值、吸附时间对焦化废水COD和色度去除率的影响,通过正交试验设计优化了工艺条件得到最优工艺方案,最后采用SEM-EDX对比分析了焦粉使用前后的形貌变化及表面元素分布。结果表明:焦粉投加量从40 g/L增至120 g/L时,COD和色度去除率显著提高;焦粉投加量大于120 g/L时,两者去除率增速减缓,投加量超过200 g/L后,两者去除率基本稳定。焦粉粒径超过5～6 mm后,COD和色度去除率基本稳定不变。焦化废水p H值调节至8附近时,两者去除率达到最大值。吸附时间从0. 5 h逐渐增加到2. 5 h时,COD和色度去除率显著提高;超过2. 5 h后,两者去除率基本稳定。通过L18(37)正交设计试验设计优化的最佳方案为焦粉投加量200 g/L,焦粉粒径5～6 mm,溶液p H值8,吸附时间3 h;在优化条件下的多次平行试验表明,COD平均去除率达到66. 8%,色度平均去除率达到71. 2%。SEM-EDX表征显示,吸附前,焦粉孔径大,表面有较大缝隙,吸附后孔径和缝隙明显减小,分析原因可能是有较多物质附着在焦粉表面及孔道内造成。吸附后焦粉表面碳、氧、硫、氮元素相对含量大幅增加,这说明焦粉对焦化废水中的有机物和部分含硫、含氮物质具有较好的吸附性能。 Abstract:In order to solve the unqualified discharge standard of coking plant wastewater after conventional biochemical treatment,the coke powder produced by the coking plant was used in the advanced treatment of biochemical effluent in the wastewater treatment process of coking plant.The effects of coke powder dosage,solution pH value,particle size,and adsorption time on the removal rates of COD and chroma in coking wastewater were investigated.The optimal process plan was obtained by orthogonal experimental design,and the morphology and surface element distribution of coke powder before and after use were analyzed by SEM-EDX.The results show that the removal rates of COD and chroma increases significantly when the coke powder dosage increases from 40 g/L to 120 g/L.To further increase the coke powder dosage,the increase of the removal rates of both COD and chroma are slow down and then remained stable when the dosage of coke powder is more than 200 g/L.When the size of coke powder exceeds 5-6 mm,the removal rates of COD and chroma are stable,and the removal rates of both reach the maximum with solution pH value of 8.Besides,the removal rates of COD and chroma improve remarkably when the adsorption time prolonges from 0.5 h to 2.5 h and then will be stable as the adsorption time further increased.The optimum design of dosage of coke powder,the diameter of coke powder,the pH value and the adsorption time are 200 g/L,5 mm,8 and 3 h,respectively,based on the L18(37) orthogonal design.The results of several parallel experiments in the optimized conditions show that the average removal rates of COD and chroma are 66.8%,and 71.2%,respectively.The SEM-EDX characterization results show that the pore size of coke powder is large,and there are large cracks on the surface before adsorption.While the pore size and cracks are obviously reduced due to the adhesion of abundant substances to the surface and pore channel of coke powder after adsorption.The