Rare-earth oxides modified Mg-Al layered double oxides for the enhanced adsorption-photocatalytic activity

Mg-Al layered double oxides (LDO) nanosheets were modified by rare-earth oxides such as La2O3, Sm2O3, and Er2O3 (M/Mg-Al, M = La, Sm, and Er) via a one-pot hydrothermal route for the solar-light induced adsorption-photocatalytic degradation of tetracycline hydrochloride (TCH). These rare-earth oxides can greatly enhance the adsorption-photocatalytic activity of Mg-Al based composites, especially La2O3. It's attributed to the efficient adsorption of vacant sites and the rapid transfer and separation of charge carriers at the junction interface. The La2O3 content, pH value, and inorganic ions intensively affect the adsorption-photocatalytic performance of La/Mg-Al. The optimal 2-La/Mg-Al with the La203 content of 4.35 % exhibits the best removal efficiency of TCH and the excellent photocatalytic durability. The removal efficiency of TCH (100 mg L-1) is 99.87 % within 110 min, and reduces to 95.88 % after five cycle times. The adsorption isotherms and kinetic behaviors of M/Mg-Al (M = La, Sm, and Er) for TCH removal are well described by Langmuir isotherm and second-order model, respectively. The active radicals such as (OH)-O-center dot and O-center dot(2)- are responsible for the solar light driven photocatalytic degradation of TCH.