A versatile Fe²⁺/urea hydrogen peroxide advanced oxidation process for not only organoarsenic remediation but also nitrogen supplement in soil

Organoarsenics in soil urgently desired careful remediation. Unfortunately, it did not receive enough attention. Herein, we report a versatile Fe²⁺/Urea Hydrogen Peroxide (UHP) process for not only organoarsenic remediation but also nitrogen supplement in soil. Insight mechanism was firstly studied in water. Roxarsone (ROX) was efficiently degraded by 99.6% following a kinetics of v= 33.91 × [ROX]× [UHP]^1.2175 × [Fe²⁺]^1.8990. Aromatic ring cleavage of ROX was realized, resulting in a satisfying mineralization performance. After degradation processes, 88.5% of total arsenic was removed from the solution at pH 5.0 via adsorption processes by generated Fe(OH)₃ particles. The particles showed much higher adsorption capacity to inorganic arsenic species than that to organoarsenic. The degradation of ROX facilitated the immobilization of total arsenic. The remediation was further carried out in soil. Satisfying removal of ROX (95.5%) and immobilization of total arsenic (89.3%) was achieved. More importantly, 94.2%− 94.6% less arsenic was transferred into the lettuce. By the injection of Fe²⁺/UHP, a sixteen times higher concentration of total nitrogen was achieved. The growth of lettuce was significantly promoted due to the multi-functions including arsenic immobilization and nitrogen supplement. The achievements suggested Fe²⁺/UHP system potentials in applications for organoarsenic remediation in soil and also soil amelioration.