疏水性分子筛对焦化废水生物处理尾水的吸附过程解析

采用表面活性剂为模板剂常温一步合成疏水性介孔分子筛(MCM-41-dry)和通过煅烧去除模板剂得到亲水性介孔材料(MCM-41-cal).分别以制备的两种分子筛作为吸附剂吸附焦化废水生物出水中COD和TOC组分,考察吸附剂浓度、pH值等对吸附过程的影响,并对吸附过程进行动力学拟合.结果表明,MCM-41-dry的吸附效果远远强于MCM-41-cal,归因于含有模板剂的材料表面具有较强的疏水性及含有高吸附容量的季铵基团.在25℃、吸附剂浓度为2g·L-1时,MCM-41-dry对焦化废水中COD和TOC的去除率分别达53%和66%,吸附量分别为64mg·g-1和17mg·g-1.拟二级动力学模型能够真实反映整个吸附过程.水样吸附前后的GC/MS数据表明,焦化废水生物出水中残留了长链烷烃、卤代物、多环芳烃等难降解有机物,经MCM-41-dry吸附后,各种物质浓度均得到降低,MCM-41-dry尤其对疏水性烷烃类有较好的吸附效果,表明该吸附剂能够优先吸附疏水性物质.此外,吸附剂对水具有一定的润湿性能,能与废水充分接触,从而利于其吸附水中的污染物,这使其用于实际废水的处理成为可能.

Adsorption mechanism of biologically treated coking wastewater by hydrophobic molecular sieves

Surfactant structure-directing agent was used to synthesize hydrophobic molecular sieve(MCM-41-dry) at room temperature and hydrophilic mesoporous material(MCM-41-cal) was prepared by removing the template with calcination.The adsorption properties of these two materials toward the organic pollutants in biologically treated coking wastewater were studied.The effects of adsorbent concentration and pH on the adsorption process as well as the kinetics of adsorption process were investigated.The adsorption capacity of MCM-41-dry was much higher than that of MCM-41-cal,which was due to its higher hydrophobicity and the existence of the quaternary ammonium groups on the surface of MCM-41.At 25 ℃,when the adsorbent concentration was 2 g · L-1,the COD and TOC removal efficiencies on MCM-41-dry toward coking wastewater were 53% and 66%,corresponding to the adsorption capacity of 64 mg · g-1 and 17 mg · g-1,respectively.The kinetic data could be fitted well by second-order kinetic model.The GC/MS data showed that the residuals of biologically treated coking wastewater were long-chain alkanes,halides,polycyclic aromatic hydrocarbons and other refractory organic compounds.After the adsorption by MCM-41-dry,these substances were reduced,especially the hydrophobic alkanes,indicating that this adsorbent could preferentially adsorb the hydrophobic substances.Meanwhile,the overall hydrophobic material still showed some hydrophilicity,which did not affect its contact with wastewater,making the practical wastewater treatment possible.