Application of chitosan as an adsorbent to treat rice mill wastewater--mechanism, modelling and optimization

The objectives of the present study is to investigate the chitosan as an adsorbent to treat rice mill wastewater under different process conditions such as agitation time (2-6 min), initial pH (2.5-6.5), chitosan dose (400-800 mg/l) and settling time (10-30 min) in order to study the removal efficiency of chemical oxygen demand (COD) and total suspended solids (TSS). The results showed that, all process variables have significant effect on the removal efficiencies. The optimum process conditions were determined (agitation time of 4 min, initial pH of 4.5, chitosan dose of 600 mg/l and settling time of 20 min) and showed high removal efficiencies (COD: 98% and TSS: 95%). FT-IR spectrophotometry was used to analyze and confirm the adsorption process. From the experimental data, Box-Behnken design (BBD) was used to develop the second order polynomial models with high coefficient of determination values (COD: 0.991 and TSS: 0.989).