Recovery of Chromium(III) Ions from Aqueous Solution by Carboxylate Functionalized Wool Fibres

The application of wool fibres for recovery of heavy metal ions is equivalent to the use of one waste to clean-up of another. A carboxylate functionalized wool fibre (PAA-g-Wool) was prepared by grafting poly(acrylic acid) onto the surface of wool fibre in the presence of potassium permanganate and oxalic acid as a redox initiator system. The graft percentage was 80.2%. The PAA-g-Wool adsorbent was applied to absorb chromium(III) from aqueous solutions in a batchwise manner. The optimum pH for recovery of chromium(III) by PAA-g-Wool was found to be 6.0. Kinetic studies show that the sorption process agrees with the pseudo-second-order kinetic model, with the correlation coefficient (R-2) more than 0.99. The adsorption equilibrium of chromium(III) was well defined by the Langmuir isotherm equation, and the adsorption capacity was found to be 95.78mg/g calculated by the Langmuir isotherm equation. After recycling for 5 times, the adsorption capacity of PAA-g-Wool to chromium ions was still maintained at 90%. The PAA-g-Wool could recover 97.1% of chromium(III) ions in the tannery wastewater.