Phosphate recovery with granular acid-activated neutralized red mud:Fixed-bed column performance and breakthrough curve modelling

摘要

Granular acid-activated neutralized red mud(AaN-RM)has been successfully prepared with good chemical stability and physical strength.However,its potential for industrial application remains unknown.Therefore,the performance of granular AaN-RM for phosphate recovery in a fixed-bed column was investigated.The results demonstrated that the phosphate adsorption performance of granular AaN-RM in a fixed-bed column was affected by various operational parameters,such as the bed depth,flow rate,initial solution pH and initial phosphate concentration.With the optimal empty-bed contact time(EBCT)of 24.27 min,the number of processed bed volumes and the phosphate adsorption capacity reached 496.95 and 84.80 mg/g,respectively.Then,the saturated fixed-bed column could be effectively regenerated with a0.5 mol/L HCl solution.The desorption efficiency remained as high as 83.45%with a low weight loss of 3.57%in the fifth regeneration cycle.In addition,breakthrough curve modelling showed that a 5-9-1 feed-forward artificial neural network(ANN)could be effectively applied for the optimization of the fixed-bed adsorption system;the coefficient of determination(R^2)and the root mean square error(RMSE)evaluated on the validation-testing data were 0.9987 and 0.0183,respectively.Therefore,granular AaN-RM fixed-bed adsorption exhibits promising potential for phosphate removal and recovery from polluted water.