预氧化/超滤组合除锰工艺的膜污染特性

针对饮用水除锰问题,对比研究了次氯酸钠(NaClO)、二氧化氯(ClO₂)和高锰酸钾(KMnO₄)3种氧化剂预处理后与超滤组合的除锰效果和膜污染特性。结果表明,3种组合工艺均能有效去除Mn²⁺,出水Mn²⁺浓度均在5μg/L以下,去除率达到99%以上。超滤膜表面的滤饼层是造成膜污染及膜通量快速下降的重要原因之一。扫描电镜(SEM)分析发现,不同氧化剂预处理后膜表面的滤饼层形态有显著不同,KMnO₄预处理后滤饼层颗粒较大,颗粒间的空隙较为明显;而ClO₂和NaClO预处理后滤饼层颗粒细小且含量少,颗粒间的空隙不明显,从而形成较为致密的滤饼层。由X射线光电子能谱(XPS)和傅里叶变换红外光谱(FT-IR)分析可知,滤饼层的主要成分是Mn³⁺和Mn⁴⁺的混合物,滤饼层表面含有丰富的表面羟基,其对水中游离的Mn²⁺表现出极强的配位吸附作用。

Membrane Fouling Characteristics of Pre-oxidation/Ultrafiltration Combined Process for Manganese Removal

In order to remove manganese from drinking water,the effect of ultrafiltration after pretreatment with three oxidants(NaClO,ClO2 and KMnO4)on removing manganese and characteristics of membrane fouling were studied.Mn^2+could be effectively removed by the three combined processes,and the concentration of Mn^2+after ultrafiltration was less than 5μg/L with the removal efficiency of more than 99%.The filter cake layer on the ultrafiltration membrane surface was one of the important reasons for the membrane fouling and the rapid decrease of membrane flux.It was found by SEM that the morphology of the filter cake layer on the membrane surface was significantly different after pretreatment with different oxidants.The particle size of the filter cake layer after pretreatment of KMnO4 oxidation was larger,and there was obvious space between the particles.However,size and content of the particles in the filter cake layer after pretreatment with ClO2 and NaClO were small and low,and the space between the particles was not obvious,thus forming a relatively dense filter cake layer.According to the analysis of XPS and FT-IR,the main components of the filter cake layer were mixture of Mn^3+and Mn^4+.The surface of the filter cake layer was rich in hydroxyl groups,which had a strong coordination adsorption effect on the free Mn^2+in water.