One-Step Synthesis of Recyclable Ti-Doped Porous SiO_2 Microspheres with Superior Structural Stability for Cationic Dye Adsorption

摘要

Dyes are hazardous to public health and the environment.Herein,we synthesized Ti-doped porous SiO_2 microspheres utilizing a one-step sol-gel method as an effective adsorbent for the removal of cationic dyes from wastewater.The study of the varying individual parameters such as titanium-sil-ica ratio,pH,adsorbent dose,and dye concentration indicated that the adsorption of methylene blue(MB)by Si_3TiO_10 microspheres exhibited excellent perfor-mance,including a wide range of applications(pH=4-11),fast adsorption rate(15 min removed 90.8％of MB),high adsorption capacity(215.29 mg/g),excel-lent selectivity(adsorption capacity toward cationic dyes(98％)and＜5％toward anionic dyes),easy des-orption steps,steady performance and multiple cycles(10 times).In addition,the adsorption process of MB by microspheres is consistent with the proposed sec-ond-order kinetic model(R~2=0.999)and Langmuir isothermal model(R_L~2=0.997).With the assistance of FT-IR,XRD,XPS,BET,SEM,and TG-DTG tech-niques,it was demonstrated that the great pore size(8.15 nm)and large specific surface area(267.97 m~2/g)of the microspheres could promote the con-tact between the active site and MB,thus achieving efficient removal of MB by using hydrogen bonding and electrostatic attraction.Furthermore,the unique spherical mesoporous structure,and the Si-O-Ti bond formed by the Ti doping rather than via simple wrap-ping and adhesion modification,which also ensured the stability of the microspheres during multiple cycles and the desorption process.