Researching On New Nano Iron And Aluminum Content Of As(Ⅲ) Adsorption Performance And Mechanism

Excessive amounts of arsenic in the water can bring a series harm. Which the harm degree is also owing to the different valence state, the toxicity of arsenite containing As（Ⅲ） can be over 30 times more than arsenate containing As（Ⅴ）. This paper research the factors affecting the adsorption of arsenic in aqueous solution, the adsorption characteristics and desorption regeneration of nanometer zero-valent iron（NZVI）, nano iron carbonyl（nano FeOOH）, nano hydroxy aluminium（nano AlOOH） and nano ferroferric oxide（nano Fe₃O₄） systematically by batch experiments. By observing the electron microscope scanning microscopic structure of adsorbents, analyzing adsorption process dynamics, isotherm and the desorption regeneration, the paper studied further the adsorption mechanism of the nano iron and aluminum series materials. In this paper the results of the study are summarized as follows:（1） Nanometer zero-valent iron can rapidly adsorb As（Ⅲ） from water within 120 min. Removal rate of As（Ⅲ） reached 98.8% at equilibrium state, the maximum adsorption capacity of 20.83 mg/g. The adsorption balance time of nano FeOOH was achieved within 4 h, the removal efficiency of As（Ⅲ） was 92%. Nano hydroxy aluminium balance was achieved within 8 h with removal efficiency of 70%. The balance removal rate of As（Ⅲ） adsorbed on Fe₃O₄ nanoparticles was relatively poor adsorption effect of 60%. NZVI adsorption optimum pH value 6.0, and nano FeOOH adsorption optimum pH value 5.0. So As（Ⅲ） was more easily absorbed on NZVI and nano FeOOH under acidic conditions. While the adsorption effects of Fe₃O₄ nanoparticles and nano AlOOH were best in neutral condition. The order of As（Ⅲ） removal capacity of four kinds of adsorbents as following: NZVI > nano FeOOH > nano AlOOH > nano Fe₃O₄.（2） Adsorption kinetics and isotherm simulation of four kinds of materials show that NZVI, nano FeOOH and nano Fe₃O₄ adsorption process conforms to the pseudo second order dynamic model, while nano AlOOH adsorption process conforms to the Elovich kinetics model. NZVI, nano FeOOH and nano AlOOH accord with Freundlich isotherm model, nano Fe₃O₄ isothermal adsorption data fits Langmuir model best.（3） Researching on the effects of coexisting anions on adsorption show that: carbonate ions and nitrate ions can strongly inhibit As（Ⅲ） adsorbed on NZVI; Phosphate ions and carbonate ions can strongly inhibit As（Ⅲ） adsorbed on nano FeOOH; Oxalate ions can promote Fe₃O₄ nanoparticles adsorption, but phosphate ions could suppress Fe₃O₄ nanoparticles adsorption. The stronger strength of the NaCl ions in water, the greater interference on nano AlOOH adsorption.（4） Adsorbent regeneration experiment showed As（Ⅲ） may form a stable chemical bond with NZVI. NZVI is difficult to be regeneration, revealing that the adsorption performance is stable. The regeneration performance of nano FeOOH, nano Fe₃O₄ and nano AlOOH were good. They still had good adsorption effects after adsorption and regeneration many times, indicating the three kinds of materials can be recycled.