Iron Recovery from Water of Acid Sulfate Soil Using Fixed-bed Cation Exchange: an Optimization Study

The Design Expert 12 software was used to optimize the recovery of iron from naturally iron alum water by ion exchange using a fixed bed column of 225H resin (India). This method also showed the ability to recover aluminum, calcium, and magnesium from water. At first, the study found suitable values of parameters such as cation exchange resin bed height of 80 cm, pH 6.5, and flow rate of 30 L h-1 by examining each individual parameter based on the evaluation of iron removal efficiency in water. Then, the optimization process was carried out with an initial iron content (iron content in natural iron-alum water before passing through the column) of 8.25±0.18 mg L-1. The optimal conditions were found through Design Expert 12 software with the values of parameters such as 80 cm (height of ion exchange resin layer), 6.5 (pH value), and 30 L h-1 (flow rate through the column). This was consistent with the conditions found initially (investigating each individual parameter) with an output iron content in the water of 0.5 mg L-1. The actual tested output iron content was less than 0.5 mg L-1, with a treatment efficiency of about 94%. The output iron concentration was below 0.5 mg L-1 with a treatment efficiency of over 93% (the actual iron ion content after treatment was 0.25-0.35 mg L-1 compared to the result from the predicted model of 0.49 mg L-1). Besides the ability to remove iron, other ions such as aluminum, calcium, and magnesium after passing through the column also had a relatively high treatment efficiency of over 85%. This result proved the effectiveness of iron treatment in natural iron-alum water by cation exchange with different iron contents, as well as the relevance of the model in practice.