Benzene Sulfonate Modified ZnCr-LDH and Its Enhanced Adsorption Properties for Anionic Dyes

Abstract A benzene sulfonate modified hydrotalcite (SO 3 -LDH) was synthesized by a facile one-pot hydrothermal technique, which can efficiently remove methyl orange (MO), Congo red (CR) and orange II (OII) from aqueous solution. After modified by benzene sulfonate, the microstructure of hydrotalcite changes obviously, from the cellular structure to the stacking structure formed by the face-face contact of hydrotalcite nanosheets, which resulted in much more exchangeable nitrate ions to remain in the interlayer space. The pre-insertion of benzene sulfonate as a pillar expanded the interlayer gallery, which facilitated the pollutant anions (MO, CR and OII) into the interlayer of LDH in the subsequent adsorption process. The maximum adsorption capacity of SO 3 -LDH for MO, CR and OII was 4200.8 mg/g, 1252.0 mg/g and 1670.6 mg/g respectively, which is approximately 1.86 times, 1.8 times and 2.32 times that of the pristine NO 3 -LDH, respectively. The removal mechanism of anionic dyes was determined as anion exchange between NO 3 − ions and dye molecules. The adsorption behavior for MO and OII is multilayer adsorption, while the adsorption behavior for CR is monolayer adsorption. The adsorption process mainly was controlled by the chemical bonding between the dye molecules and adsorbent active sites. The benzene sulfonate modified LDH has a great potential to be used as a high-efficient adsorbent to remove anionic dyes from aqueous solution.