Production of adsorbents based on sunflower husks for removal of chromium (VI) from wastewater

At present, industrial and agricultural waste is often used as sorption materials for water remediation. Adsorbents obtained from sunflower husks were used for wastewater treatment from chromium (VI) ions. Studies were carried out using unmodified and modified sunflower husk and a model wastewater solution containing 10 mg/dm3 of chromium (VI) ions. Solutions of acids (H2SO4, HNO3, HCl, H3PO4) and alkalis (KOH, NaOH) were used to modify sunflower husks. The maximum sorption capacity was revealed in sunflower husks treated with sulfuric acid; thus, this modifying agent only was used in further experiments. The modification was carried out using 1–4 M solutions of H2SO4 at 30–75 °C for 30–120 min. The research results showed that the acid treatment of sunflower husks is more effective than that using alkalis. The sorption capacity of the modified sunflower husk increased up to the concentration of sulfuric acid of 3 M, followed by a further decrease. A full factorial design having 3 factors of the experiment was set, which allowed the maximum sorption capacity to be identified. The optimal modification procedure was as follows: sunflower husks are treated using 2.5 M sulfuric acid solution at 60 °C for 30 min, washed with distilled water and dried at 105 °C to a constant weight. Studies showed that adsorbents obtained from sunflower husks can be used to remove chromium (VI) ions from wastewater.