Chitin-humic acid hybrid as adsorbent for Cr(III) in effluent of tannery wastewater treatment

Adsorption of Cr(III) from both synthetic and real samples of tannery wastewater treatment's effluent on chitin-humic acid (chitin-HA) hybrid has been carried out. Rate constant and capacity of adsorption of Cr(III) from the synthetic sample were investigated and removal of Cr(III) from the real sample was tested at optimum medium acidity equivalent to pH 3.5. Characterization using Fourier transform infra red (FT-IR) spectroscopy revealed that both COO⁻ and N-acetyl originated from respectively humic acid (HA) and chitin were involved on the adsorption of Cr(III), and hence the Freundlich's multilayer and multi-energy adsorption model was more applicable to treat the adsorption data than the Langmuir's monolayer and mono-energy model. The quantification of adsorption capacity and rate constant using Freundlich isotherm model and first order adsorption reaching equilibrium yielded values of 6.84 × 10⁻⁴ mol g⁻¹ (35.57 mg g⁻¹) and 1.70 × 10⁻² min⁻¹, respectively. Removal test for the real wastewater treatment's effluent showed that the maximum amount of Cr(III) could be removed by 1 g of chitin-HA hybrid was 2.08 × 10⁻⁴ mol or equivalent to 10.82 mg.