A novel bisphosphonate-based solid phase method for effective removal of chromium(iii) from aqueous solutions and tannery effluents

Effective removal of chromium(iii) from waste waters e.g. in the leather industry is required due to continuously tightening environmental regulations, and several methods such as precipitation and adsorption are currently in use. Nevertheless, more efficient, straightforward and inexpensive methods are constantly being sought. The current study describes a novel method to separate chromium(iii) from aqueous solutions based on the use of solid bisphosphonates with a P-C-P backbone. Five classes of bisphosphonates with different functional groups and alkyl chain lengths at the center carbon, in all 16 compounds, were prepared and their suitability for metal ion complexing as chelating agents was investigated. Two of the studied compounds, which were almost insoluble in water, were effective in removing chromium(iii) quantitatively from aqueous solutions and real waste water samples of tanneries. The results obtained were also compared to the commercially available Diphonix super( registered ) resin.