氟化钠改性膨润土的结构及对二次纤维的助留助滤效果

Morphology of Sodium Fluoride Modified Bentonite and Its Retention and Drainage Efficacy Secondary Fibers

采用中性改性剂氟化钠(NaF)对钙基膨润土进行改性,分析了改性土的结构形态及其助留助滤效果。X射线衍射分析表明,在NaF用量4%时可以将膨润土中的Ca^(2+)交换完全。与常规Na_2CO_3改性膨润土相比,NaF改性膨润土呈完全剥离的片状结构,具有更好的胶体与分散性能,粒度小、悬浮液流动性好且对二次纤维浆料具有更好的助留助滤效果,尤其是放置28d后仍能保持良好的助留助滤效果。各种改性膨润土的物化性能与助留助滤效果均与钠改性剂的用量有关,且在膨润土刚好完全钠化时助留助滤效果最好。

XRD analysis shows that calcium ions in the layers of bentonite are replaced completely by sodium ions when 4% of sodium fluoride （based on the weight of bentonite） is used as ion-exchanger. The morphology of the bentonite and its suspension properties were observed and evaluated by TEM and conventional analysis methods respectively. It was found that the sodium fluoride-modified bentonite is dispersed as single layered structure and exhibits better suspensibility and dispensability, smaller particle size as well as lower dispersion viscosity compared with sodium carbonate-modified bentonite. Naturally, the bentonite modified by sodium fluoride has better retention and drainage efficacy in secondary fibers compared with the bentonite modified by sodium carbonate; especially it can sustain its good performance even after four weeks＇ storage as a suspension. The suspending and dispersing properties as well as retention and drainage effiiciency of the modified bentonite in secondary fibers are related to the dosage of the ion-exchangers. The greater improvement on the retention and drainage of the secondary fibers occurs when the calcium ions in the layers of the bentonite are just completely exchanged by the sodium ions of the ion-exchangers.