Comparison of attrition in citric acid modified soybean hulls and commercial cation exchange resins

The integrity of ion exchange media used under conditions of different time s of use, temperatures and pH values is important in its selection. This st udy was conducted to quantify the lack of integrity (attrition) in base-ext racted (BE), citric acid (CA)-modified soybean hulls, a lignocellulosic cat ion exchange material and compare its attrition to two synthetic, commercia l cation exchange resins. Attrition was determined in both batch and column operations. Batch studies included measuring attrition over a 23 h period under conditions of constant pH, variable pH and at different temperatures. Under conditions of a constant pH of 4.8, 25 degreesC and using a stir bar , modified hulls had mostly lower attrition than the two commercial product s. Under acidic conditions, modified hulls demonstrated very low ( < 5%) at trition. At alkaline pH values, modified hulls had higher attrition than th e resins after 24 h of stirring at 25 degreesC. Although attrition increase d at alkaline pH, the modified hulls ability to bind copper ion (Cu2+) was unaffected by FH. After 74 h shaking at 65 and 85 degreesC, modified hulls also had greater attrition than the synthetic polymers. At these temperatur es, a decreased ability of the modified hulls to bind copper ion was observ ed compared to the lower temperatures of 25 and 45 degreesC. When the produ cts were compared in column experiments at 25 degreesC, all materials had l ow ( < 10%) attrition. Our studies indicate that in terms of product integr ity, modified soybean hulls could be useful in several applications requiri ng a metal ion adsorbent, bur not necessarily at high temperatures. (C) 200 1 Published by Elsevier Science B.V.