Efficient removal of As (Ⅲ) by a La/Fe composite membrane filter: The composite form of La, the dynamic adsorption and adaptability

Abstract

Arsenite (As(III)) has higher toxicity and removal difficulty. Herein, three nanocomposite adsorbents (La(OH)3-Fe3O4, La2O3-Fe3O4, and LaxFe3-xO4) were prepared for As(III) adsorption removal to investigate the optimal form of Fe3O4-lanthanum composites. The materials were characterized by SEM, TEM, XRD, FT-IR, etc. The adsorption results showed that the maximum adsorption capacities (Qmax) of As(III) by La(OH)3-Fe3O4(1:1), La2O3-Fe3O4(1:2), and La0.15Fe2.85O4 were 148.15, 120.60 and 161.22 mg/g, respectively. In addition, the removal efficiency of La0.15Fe2.85O4 for As(III) could still reach 96.01% after 10 cycles, showing the good regeneration ability and stability. The kinetic and isotherm models showed that the adsorption process conformed to the pseudo-second-order and Langmuir isotherm models. Furthermore, the adsorption mechanism of La0.15Fe2.85O4 for As(III) was analyzed by X-ray photoelectron spectroscopy. To improve the practical application of La0.15Fe2.85O4, a composite nanofiber membrane (La0.15Fe2.85O4/PAN) was prepared, and the As (III) removal efficiency of the membrane was investigated by static and dynamic adsorption through building a membrane filter. The results showed that La0.15Fe2.85O4/PAN had high Qmax (94.66 mg/g), good regeneration ability and anti-interference ability. The results of dynamic adsorption indicated that La0.15Fe2.85O4/PAN with a diameter of 25 mm could reduce 535 mL of As(III) solution with an initial concentration of 50 μg/L to 10 μg/L at a flow rate of 0.5 mL/min under pH 7, indicating the membrane reactor had good processing capacity. This study confirmed the most favorable form of La-Fe composite for arsenic adsorption, and provided a composite membrane technology to realize its practical application for water treatment.