Sustainable sorption strategies for removing Cr(3+) from tannery process wastewater

Two different strategies for the removal of trivalent chromium (Cr(3+)) from contaminated water are reported. The first one is based on the sorption process on an organo-mineral complex, named LDH-HP, obtained in turn by sorption of polymerin, the humic acid-like fraction occurring in olive oil mill wastewater, on a layered double hydroxide (LDH) of magnesium and aluminium with carbonate in the interlayer. This sorption process is preliminary developed on simulated wastewater (SW) as theoretical model and successively applied on tannery process wastewaters (TPWs) natively containing Cr(3+). The removal of Cr(3+) from TPW is lower than that observed for SW, because of the large compositional variability of TPW. The second one is based on the direct production of a LDH of magnesium and chromium (Cr(3+)), using as starting material TPW, naming LDH-TPW the complex produced. This process allows the complete removal of Cr(3+) from TPW and also the abatement of chemical oxygen demand, indicating to be a very promising purification process for an industrial application.