Modeling chromate removal using type 1 quaternary amine anion exchangers in drinking water applications

Chromates have wide applications in the industry as corrosion inhibitors and oxidizing agents in various reactions. Unfortunately, they are carcinogenic at low concentrations. The chromates can be removed by quaternary amine anion exchangers. Using a series of collected data from literature, a dynamic Thomas isotherm was used to model and subsequently predict the effect of contact time, initial capacity, and anion exchange characteristics on the performance of the resin system. The parameters of the model were derived via a non-linear programming algorithm where the objective function was the minimization of the least square errors between experimental and predicted values. The resulting model was used to predict the performance by instituting a major increase in chromate concentration up to 200 ppb. This demonstrated that the Thomas model can be used to accurately predict the resin performance in chromate removal even in the presence of competing ions like chlorides and sulfates.