Abstract: There are strict regulations on the discharge of Zn(Ⅱ) wastewater in China. Among adsorptive material that can efficiently remove Zn(Ⅱ) from wastewater, palygorskite (PAL) is considered to be a promising adsorptive material. To verify the effect of humic acid (HA) on the adsorption of Zn(Ⅱ) by PAL, static adsorption experiments were carried out to compare the adsorption rates of Zn(Ⅱ) by humic acid/palygorskite (HA/PAL) and pure PAL, and the performance and mechanism of removing Zn(Ⅱ) from aqueous solution by PAL and HA/PAL were studied. The adsorption equilibrium time of PAL was 120 min, and temperature had little effect on the adsorption process, and the adsorption rate of Zn(Ⅱ) by PAL increased with the increase of the dosage and the decrease of the Zn(Ⅱ) initial concentration. The adsorption equilibrium of HA/PAL was reached at 120 min, and the adsorption process of Zn(Ⅱ) by HA/PAL was also not affected by temperature, and the increase of the dosage and the decrease of the Zn(Ⅱ) initial concentration improved the adsorption rate of Zn(Ⅱ) by HA/PAL. The adsorption process of Zn(Ⅱ) by PAL fitted the Langmuir model, and the pseudo-first-order kinetic model could better fit the experimental data of PAL. However, the adsorption process of Zn(Ⅱ) by HA/PAL was more consistent with Freundlich model, and the pseudo-first-order kinetic model also better fitted the experimental data of HA/PAL. According to thermodynamic parameters, the adsorption of Zn(Ⅱ) by PAL and HA/PAL is endothermic. Under the same conditions, the adsorption rate of Zn(Ⅱ) by PAL is higher than that of Zn(Ⅱ) by HA/PAL, and the influence of all experimental conditions on PAL is greater than that of HA/PAL. The characterization results of SEM, BET and FTIR showed that HA was successfully loaded on PAL surface and reduced PAL specific surface area.

Key words: Zn(Ⅱ), humic acid, palygorskite, isotherm, kinetic, thermodynamic