Electrochemical crystallization for recovery of phosphorus and potassium from urine as K-struvite with a sacrificial magnesium anode

• Published in: Environmental chemistry letters Vol. 20; no. 1; pp. 27 - 33
• Main Authors: Shan, Jinhua, Liu, Hongbo, Long, Shiping, Zhang, Haodong, Lichtfouse, Eric
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.02.2022; Springer Nature B.V; Springer Verlag
• Subjects: Agricultural sciences; Analytical Chemistry; Anodes; Circular economy; Continental interfaces, environment; Crystallization; Crystals; Current density; Earth and Environmental Science; Earth resources; Ecotoxicology; Electrochemistry; Environment; Environmental Chemistry; Environmental Engineering; Environmental Sciences; Fertilizers; Food and Nutrition; Geochemistry; Life Sciences; Magnesium; magnesium ammonium phosphate; Original Paper; Phosphates; Phosphorus; Pollution; Potassium; Prefabrication; Recovery; Sciences and technics of agriculture; Sciences of the Universe; Side reactions; Struvite; Urine; Wastewater; Urine; Sacrificial anode; Electrochemical crystallization; Struvite; Nutrient recovery
• ISSN: 1610-3653; 1610-3661
• DOI: 10.1007/s10311-021-01333-5

Declining earth resources, rising ore cost and increasing pollution are calling for recycling of wastewater in the context of the circular economy. In particular, urine is a potential source of phosphorus (P) and potassium (K), yet currently available methods for P and K recovery are limited in efficiency. Here, we designed an electrochemical crystallization system using sacrificial magnesium anodes to recover P and K in the form of K-struvite (MgKPO 4 ·6H 2 O) from simulated urine at low (P/K = 0.25) and high (P/K = 0.6) phosphate levels, respectively. Results show optimal recoveries of 88.5% for P and 35.4% for K in the form of rod-shaped K-struvite at 3.5 mA/cm 2 , though higher current density reduced recovery due to side reactions and pH increase. Seeding prefabricated struvite crystals at 1.6 g/L into urine enhanced the recovery of K by 14.7% and of P by 23.7% compared to the control group. Overall, our findings show that electrochemical crystallization is promising to recover K-struvite fertilizers.