通量对膜法除锰工艺净水特性及阻力变化的影响

Effect of Flux on Manganese Removal and Hydraulic Resistance in a Membrane-based Manganese Removal Process

超滤工艺在处理含锰原水时,膜表面会沉积具备催化功能的锰氧化物,形成锰质活性滤饼层,该滤饼层在具备一定催化除锰效果的同时,也带来了严重的膜污染。为了更好地利用锰质活性滤饼层,提升超滤工艺的除锰性能,考察了通量为5、10、15和20 L(/m^(2)·h)时超滤系统中活性滤饼层对Mn^(2+)的去除效果及阻力变化趋势。结果表明,在5 L(/m^(2)·h)通量条件下,锰质活性滤饼层既保证了对Mn^(2+)的高效去除,又维持了较低的过滤阻力;而高通量的活性滤饼层的过滤阻力则迅速增长。在对活性滤饼层的组成和形貌进行分析后发现,低通量条件下,滤饼层中锰氧化物的粒径更大,结构也更加疏松,因此维持着低阻力。由于锰氧化物的接触氧化作用,其自身能够形成团块,使滤饼层表现出非均质的结构;与高通量相比,低通量条件下较长的接触时间使该结构更易形成和保持,从而极大地减缓了水力阻力的增加。

In an ultrafiltration process,manganese oxides with catalytic activity are deposited on the membrane surface to form an activated cake layer,which has catalytic ability to remove manganese.However,the cake layer can cause severe membrane fouling.To better utilize the activated cake layer to enhance the Mn^(2+)removal,the effect of Mn^(2+)removal by activated cake layer and the resistance trends in ultrafiltration system were investigated at fluxes of 5 L/(m^(2)·h),10 L/(m^(2)·h),15 L/(m^(2)·h)and 20 L/(m^(2)·h).The results showed that at the flux of 5 L/(m^(2)·h),the ultrafiltration system not only achieved high Mn^(2+)removal,but also had essentially no increase in hydraulic resistance.Contrarily,the hydraulic resistance of the activated cake layer increased rapidly at high fluxes.The analysis of the composition and morphology of the activated cake layer has revealed that under low flux conditions,the particle size of manganese oxides in the cake layer was larger,and the structure was sparser.This,in turn,contributed to maintaining a low hydraulic resistance.Moreover,due to the adsorption and oxidation by manganese oxide,it could form agglomerates by itself,so that the cake layer exhibited a heterogeneous structure.This structure could be effectively formed and maintained at low fluxes,and thus greatly slowing down the increase of hydraulic resistance.