Fixed bed adsorption of phosphate by lanthanum carbonate modified microfibrous composite

A kind of novel adsorbent, lanthanum carbonate modified microfibrous composite (LC-MC), is synthesized through a facile combined wet lay-up paper making and hydrothermal synthesis method. The fixed bed phosphate adsorption results show that LC-MC performs best when initial phosphate concentration is 5 mg/L, flow rate is 2.7 mL/min and bed height is 2 cm, with the maximum breakthrough time of 82.5 h and maximum adsorption capacity of 38.5 mg/g. High bed height and low flow rate are beneficial to the phosphate adsorption. Acid solution conditions benefit the adsorption process but will cause leakage of the lanthanum species (over 8 mg/L). 50 mg/L co-existing anions have no significant effect on the adsorption process, while concentrations more than 100 mg/L obviously inhibit the adsorption. The adsorbent also shows a good regenerability with less than 15 % decrease in adsorption capacity after 5 cycling runs. The adsorption kinetic process can be described better by the Yoon-Nelson model than Adams-Bohart model and Thomas model. Finally, the mechanism study indicates that the formation of phosphate lanthanum is the main reason for phosphate adsorption on LC-MC. Results show that LC-MC is a promising phosphate adsorbent to be used in fixed bed.