本研究旨在探討軟膠體粒子之微過濾機構及壓縮性質，本研究採用三種不同葡聚醣分子量(70 kDa、500 kDa及2000 kDa)分別與過錳酸鉀交聯成葡聚醣-二氧化錳( Dextran-MnO2 )之多孔性軟膠體，此種膠體粒子會在受到壓縮後變形，並擠出內部水分。實驗結果發現，此三種不同之軟膠體雖有相近的粒徑分佈、介達電位及密度，但由於其機械強度及壓縮性質導致其過濾行為有顯著之差異：當分子量越大，粒子的壓縮變形越快達穩定，且由於分子量大的粒子越快壓縮成緻密層(skin layer)，故分子量大的粒子過濾時濾速會最慢。不同軟膠體的壓縮係數都在1左右，表示其濾餅均屬於容易被壓縮性質，故說明了本研究中增加過濾壓差，會形成較為緻密的結構，使得過濾比阻會增加。此外，本研究利用濾面上粒子之力平衡解析，探討在過濾時間與操作條件下對濾餅之成長速率的影響，發現壓力越大其成長的濾餅越厚；但掃流速度越大則成長的濾餅厚度卻不一定，主要原因為在濾餅壓縮的遲滯時間內，且在相同的操作壓差下，當濾餅層開始壓縮時，濾餅層生成的越厚，相對來說壓縮的結構較不緻密，導致之後的過濾時間，相對來說粒子較易附著，濾餅層較厚且濾速較大。而葡聚醣分子量越大，粒子的附著機率越小，導致初始濾餅易壓縮越緻密，故粒子成長厚度越薄，阻力越大。此外，並以濾餅之動態分析，分析濾餅局部過濾比阻，發現隨著過濾時間增加，濾餅不斷的成長和壓縮，導致平均過濾比阻增加，但由於不同時間下濾餅層的過濾比阻均不一樣，故平均過濾比阻不一定隨著掃流速度增加而增加。 Studies on mechanisms of compression and microfiltration of soft particles. Different kinds of Dextran–MnO2 gel particles are prepared in different conditions, depending on variables such as the molecular weight of dextran (70k Da, 500 k Da and 2000 k Da ). Dextran-MnO2 porous particles are prepared and used in experiment. This kind of colloidal particles are deformed their shape and squeezed out their inside water during compression. Experimental results show that although the mean sizes and stern potential and density of these gel particles are very close to each other, their filtration characteristics are far different due to their mechanical strength and compressibility. the deformation and compression of particles stabilize and a skin layer with compact structure forms quickly with an increase in the molecular weight of dextran. It could be said that the filtration rate decreases with an increase in the molecular weight of dextran. Different soft compression coefficient near one, result in the cake belong to easy to compress. Result proved that the pressure increase in this research, will form compact structure and specific filtration resistance increase. Causing this phenomenon that particles collect in the suspension. The probabilities of particle deposition under various conditions are estimated using the force balance model. It can be found that the cake mass and the cake increase with the increase of filtration pressure but cake increase uncertain with the decrease of cross-flow velocity. Thick of cake thickness compress less compact structure than thin of cake thickness, result in particles deposition on the membrane and filtration rate are quick after filtration time. It could be said that probability of particles deposit decreases in initial time, result in cake compress more compact structure and the filtration rate decreases with an increase in the molecular weight of dextran. The dynamic analytic method is employed to analyze of local specific filtration resistance under various conditions. Due to cake increase and compress so that local specific filtration resistance increase with the increase of filtration time. Due to cake compress with the increase of filtration time is different so that local specific filtration resistance is not increase with cross-flow velocity.
