Effect of silicon on the mathematical model prediction and adsorption mechanism of boron removal by a fixed-bed column

Abstract

To promote the practical application of a novel resin (tiron-modified resin) in the removal of toxic element boron from actual water, the dynamic adsorption of boron was investigated in the presence of silicon by a fixed-bed column. The breakthrough time, exhaustion time and adsorption capacity of the column bed decreased in the presence of silicon due to competitive adsorption. The boron adsorption capacity decreased from 5.01 mg/g to 2.91 mg/g in the mixed solution compared with the single solution containing the same initial concentration. However, the total adsorption capacity (the sum of boron and silicon) was close to that of single boron. The Thomas and Yoon-Nelson models can appropriately predict the whole breakthrough curves (BTCs) of boron and the sum of both elements during the column bed adsorption process despite the coexistence of silicon. This result will have great reference value in related fields. The mixed adsorption mechanism of boron and silicon varied from single adsorption. For boron, besides the formation of triangular and tetrahedral complexes, the B-O-Si chemical bonds were also formed. However, the silicon was mainly adsorbed via monomers, with the addition of one-dimensional linear polymer and two-dimensional sheet polymers. The presence of silicon reduced the life factor of the column bed's capability to avoid breakthrough time from 6.8 to 5.5 cycles at t = 0, but prolonged the completely exhausting time from 7.8 to 11.7 cycles. T-resin manifests itself in preferential and continuous adsorption of boron, showing enormous potentialities for controlling boron pollution in actual waters.