白云石-生物炭复合膜过滤吸附低浓度磷酸盐

Filtration and adsorption of low concentration phosphate by dolomite-biochar composite membrane

随着工农业的发展,大量磷被排入自然水体,导致水体富营养化现象的发生。传统化学法和生物法无法有效去除水中低浓度磷酸盐,将吸附剂与超滤膜相结合,通过错流过滤的方式有望捕获并吸附水中低浓度磷酸盐。将白云石改性生物炭吸附剂(DO/BB)装载于聚偏二氟乙烯(PVDF)超滤膜中制备了PVDF-DO/BB复合膜,并考察了PVDF-DO/BB复合膜的微观结构、力学性能及对磷酸盐的吸附分离性能。结果表明,与纯PVDF膜相比,PVDF-DO/BB复合膜的表面粗糙度增加,亲水性变差;拉伸强度增强约23%,柔韧性也有所提升;当初始磷酸盐质量浓度为1.0 mg/L时,经PVDF-DO/BB处理后最低可降至0.16 mg/L,且在5次吸脱附循环后去除率依然>75%。通过吸附动力学和吸附等温线模型拟合,发现吸附过程主要受单层的化学反应控制,活性位点分布均匀。结合PVDF-DO/BB吸附磷酸盐前后的XPS分析,阐明吸附机理主要包括静电引力、内层单齿络合物的形成、内层双齿络合物的形成和羟磷灰石沉淀的生成。此外,PVDF-DO/BB可高效拦截大分子污染物,具有吸附-超滤双功能。

With the development of industry and agriculture,a large amount of phosphorus is discharged into natural water bodies,leading to eutrophication in water bodies.Traditional chemical and biological methods cannot effectively remove low concentration of phosphate from water.Combining adsorbent with ultrafiltration membrane is expected to capture and adsorb low concentration of phosphate by cross-flow filtration.Dolomite modified biochar adsorbent(DO/BB)was loaded into polyvinylidene difluoride(PVDF)ultrafiltration membrane(PVDF-DO/BB).The microstructure,me⁃chanical property and phosphate adsorption/separation performance of PVDF-DO/BB were investigated.The results showed that compared with pure PVDF membrane,the surface roughness of PVDF-DO/BB composite membrane increased and its hydrophilicity deteriorated.The tensile strength of PVDF-DO/BB was increased by about 23%,and the flexibility was also improved.When the initial phosphate concentration was 1.0 mg/L,it could be reduced to 0.16 mg/L after PVDFDO/BB treatment,and the removal rate remained>75%after five adsorption-desorption cycles.Through the models fitting of adsorption kinetic and isotherm data,it was found that the adsorption process was mainly controlled by monolayer chemical reaction.The distribution of active sites was uniform.Combined with the XPS analysis of PVDF-DO/BB before and after phosphate adsorption,it was clarified that the adsorption mechanism mainly consisted of electrostatic attraction,inner sphere monodentate complex formation,inner sphere bidentate complex formation and hydroxyapatite precipitation.Moreover,PVDF-DO/BB could efficiently reject macromolecular pollutants,with the dual function of adsorptionultrafiltration.