Sodium Hypophosphite as Reduction Reagent for Cooper Ions Recovery from Aqueous Solutions

This study presents the Cu2+ recovery from aqueous solutions. The used method was based on the Cu2+ reduction with sodium hypophosphite in acid aqueous solution to poorly soluble forms. Processes run better after 15 minutes, at 90 degrees C, pH=2-6.5 and H3PO2-:Cu2+ molar ratio 5:1. H2SO4, H3PO4 and HCl were added to pH adjusting. The presence of the acids anions proved to affect the process approach and the nature of resulted compounds. The X-ray diffraction analysis and IR spectral investigation of the formed precipitates were effectuated. Using H2SO4 and H3PO4 to adjust the pH value led to Cu2+ recovery in reduced forms as Cu and Cu2O, in molar ratio Cu/Cu2O=1.62. Using HCl the reducing process was disrupted by the formation of hydroxychlorides as: anatacamite, atacamite, anthonyite and eriochalcite. The recovery efficiency of Cu2+ was determined using FAAS analyses on the soluble Cu2+ remained after the recovery process. The copper recovery efficiency in the optimal process conditions was over 99 %. The proposed procedure for copper recovery can be applied for the cleaning of waste galvanic waters. In the end, the neutralisation of the hypophosphite excess and pH in the residual waters can be done easy and cheep with calcium hydroxide.