Utilization of Modified Sunflower Seed as Novel Adsorbent for Nitrates Removal from Wastewater

The food processing waste, sunflower seed shells (SS), were chemically modified and tested as adsorbents for nitrate removal from water and wastewater. Chemical modification of the SS implied a quaternization reaction. Efficiency and mechanisms of nitrate removal from water by modified sunflower seed shells (MSS) were examined using model nitrate solution (MS) and samples of real wastewater (RW) in batch adsorption experiments while the regeneration capacity was tested by fixed bed adsorption column and regeneration experiments. The MSS had the highest nitrate adsorption capacity of 12.98 mg g-1 for model nitrate solution, 12.16 mg g-1 for model wastewater, 13.70 mg g-1 for the wastewater generated by the confectionery industry (CI), and 12.52 mg g-1 for the wastewater generated from the meat industry (MI). Equilibrium data were analyzed, and results demonstrated a better fit for the Freundlich isotherm model, while kinetic models showed that the adsorption has pseudo-second-order kinetics. Adsorption and desorption experiments in fixed bed columns showed good MSS regeneration performances and efficiency after a minimum of three cycles. Lower efficiencies of regenerated MSS were noted when real confectionery and meat industry effluent were treated. Environmental toxicity of nitrate saturated MSS was tested using an acute toxicity test with freshwater plankton Daphnia magna. SS showed very good properties and could be competitive among already known and existing "low-cost" adsorbents as potential adsorbents for nitrate removal from water and wastewater.