Application of zeolite on ammonium-rich Post-Hydrothermal liquefaction Wastewater generated from Hydrothermal Liquefaction process of Spirulina

Post-Hydrothermal Liquefaction Wastewater (PHWW) has a very high concentration of ammonium (6200 +/- 106 mg/L), which is an inhibitor for the traditional sewage treatment process. The major objectives of this study were to: (1) evaluate the capacity of ammonium adsorption from PHWW using two zeolites (natural clinoptilolite and activated clinoptilolite) as the absorbent; (2) investigate the effects of zeolite particle size (0.18 similar to 0.90 mm) and dosage (0.1 similar to 0.5 g/mL) on ammonium adsorption efficiency; (3) study the regeneration methods of the natural clinoptilolite. Results obtained from the experiments showed that the optimized particle size and dosage of the natural and the activated clinoptilolite were 0.18 similar to 0.30 mm, and 0.5 g/mL, corresponding to a highest ammonium adsorption efficiency of 51 +/-2% and 79 +/- 1%; the ammonium adsorption efficiency of zeolite was positively related to the dosage; the smaller the particle size, generally the higher the ammonium adsorption efficiency; in addition, the activated clinoptilolite had a stronger activity and a larger capacity of ammonium ion exchange; when the natural clinoptilolite was regenerated with 4 mol/L NaOH and 0.1 mol/L HCl, the former was better. Application of zeolite on ammonium-rich PHWW is an alternative solution for reducing the concentration of toxic ammonium for subsequent utilization of PHWW.