Efficient removal of nitrate using electrochemical-ion exchange method and pretreatment of straw with by-products for biological fermentation

An environmentally benign cycle system was tried to be established in this work, in which simultaneous electrochemical reduction of nitrate and adsorption of ammonia by-product with zeolite, and the pretreatment of straw using the ammonia-loaded zeolite were studied. The employment of Ti/IrO2-Pt anode and Cu/Zn alloy cathode for electrolysis, and zeolite for adsorption were efficient for nitrate removal. After treatment, the concentration of nitrate-N in treated water decreased from 100.0 to 3.6 mg L− 1 over 300 min and the ammonia by-product was completely adsorbed from treated water by zeolite, meeting the allowed limit for drinking water. Pretreatment of rice straw with the spent zeolite containing ammonia (ZCA) showed good performance in delignification and increasing the hydrolysis ratio, giving an attractive alternative for both disposal of the used zeolite and pretreatment of straw.

Research highlights
► Electrochemical reduction of nitrate and adsorption of the ammonia by-product with zeolite.
► Pretreatment of straw with zeolite containing a large amount of ammonia was studied.
► The zeolite containing ammonia (ZCA) had good performance in the pretreatment of rice straw.