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Adsorption is an economical and effective method for recovering phosphate from wastewater. In order to improve the adsorption capacity of Fe 3 O 4 for phosphate and for easy separation from water under the action of an external magnetic field, CaO 2 was used in this study as an oxidant to partially oxidize Fe 2+ . A phosphorus recovery adsorbent, Ca doped Fe 3 O 4 (CMIO), was prepared and was characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and vibrating sample magnetometer (VSM) techniques. The results showed that CMIO had a Ca 2+ doped Fe 3 O 4 crystal structure with a saturation magnetization of 38.82 emu·g -1 , which was easily separated from water by using an external magnetic field. The phosphorus adsorption capacity of the CMIO decreased with an increase of pH value. When pH=2 and T =25℃, the maximum adsorption capacity was 24.10 mg·g -1 , which is almost five times the adsorption capacity of pure Fe 3 O 4 . The phosphorus adsorption of CMIO was in accord with the Langmuir isotherm adsorption model, and the adsorption process followed the pseudo-second order kinetic model. The complexation of phosphate occurred on the inner surface of the CMIO to form a ≡Fe-Ca-P ternary complex, which can adsorb phosphorus. Compared with other anions in the aqueous solution, CMIO had good adsorption selectivity to PO 4 3- , and the adsorbed PO 4 3- could be desorbed by NaOH solution.The quality loss of the CMIO was less than 4% once, and multiple recycling was possible.

Nano zerovalent iron (nZVI) and CaO 2 were used to construct a heterogeneous Fenton-like system to degrade α -hexachlorocyclohexane ( α -HCH) in soil solution, and the degradation efficiency and mechanism were investigated. The results showed that nZVI/CaO 2 can degrade α -HCH in an extensive pH range. When the dosage of nZVI and CaO 2 was 1 g·L -1 and pH was 5, the degradation rate of α -HCH reached 93.23%. The degradation process of nZVI, CaO 2 , and nZVI/CaO 2 treatments accorded with the first-order reaction kinetics model. The reaction rate constant of nZVI/CaO 2 was greater than the sum of individual treatments, showing that nZVI/CaO 2 has a synergistic effect on the degradation of α -HCH. Through quenching free radical experiments, the contribution rate of superoxide radicals was shown to be greater than that of hydroxyl radicals. Intermediates, including trichlorobenzene and chlorobenzene, were detected. The content of trichlorobenzene showed a sharp increase initially, and then decreased quickly. The chlorobenzene content was low and showed little change. The α -HCH in the soil washing solution was first reduced to trichlorobenzene, which was further reduced to chlorobenzene or mineralized into CO 2 and water directly.