Removal of chromate by solvent impregnated resins (SIRs) stabilized by coating and chemical crosslinking. Ⅱ. Column-mode sorption/elution studies

摘要

A series of column-mode sorption/elution studies for the removal of chromate from aqueous solution at pH 4.0 have been carried out with Aliquat 336 containing solvent-impregnated resins (SIRs) coated with poly(vinylalcohol) crosslinked with vinylsulphone. The complete elution of chromate from SIRs was achieved with a mixed 1 M NaOH-1 M NaCl solution. The effect of coating and the degree of crosslinking on chemical stability of SIRs were studied by running four sorption-washing-elution-washing cycles. The chemical stability of impregnated resins was monitored after each cycle by nitrogen analysis. The decrease in nitrogen content of uncoated resins was significant after each cycle. In the case of coated SIRs, only a small decrease was observed after one cycle and, thereafter, the nitrogen content remained almost constant in subsequent cycles. In a separate study, the coated SIRs were pre-conditioned with a mixed 1 M NaOH-1 M NaCl solution prior to column-mode sorption. The nitrogen content of the pre-conditioned coated solvent impregnated resins was analyzed after four successive sorption-washing-elution-washing cycles. The nitrogen content after four cycles was almost the same as the original coated low crosslinked resin. The small decrease in nitrogen content observed after four cycles in the case of coated highly crosslinked SIRs is within the range of analytical error of nitrogen analysis. The decrease in nitrogen content of the lowest crosslinked resins was probably due to loss of extractant after four cycles.