Thiocyanate removal from aqueous solution by a synthetic hydrotalcite sol

The use of a chloride-containing synthetic hydrotalcite sol (LDHC) as adsorbent to remove thiocyanate from aqueous solution was investigated. LDHC was prepared by coprecipitation and was characterized by HRTEM, particle size, XRD, and FTIR. The experiments showed that LDHC was particularly effective in removing thiocyanate due to its small particle size and high zeta potential. The adsorption of thiocyanate on LDHC was favored when the initial solution pH was in the range 3–10, though the most effective pH range was between 4.0 and 8.0. The adsorption reached equilibrium within 150 min. The interaction between the surface sites of LDHC and thiocyanate ions may be a combination of both anion exchange and surface complexation. The pseudo-second-order model best described the adsorption kinetics of thiocyanate onto LDHC. The equilibrium isotherm showed that the adsorption of thiocyanate on LDHC was consistent with the Langmuir equation and the saturated adsorption capacity of LDHC for thiocyanate was 98.3 mg/g at 20 °C. The regenerated LDHC in FeCl3 solution can be used repeatedly in adsorption–regeneration cycles. The results showed that LDHC can be used as a new adsorbent for thiocyanate removal from aqueous solution because of its high adsorption capacity and rapid adsorption rate.

The adsorption of thiocyanate on LDHC was consistent with the Langmuir equation and the saturated adsorption capacity of LDHC for thiocyanate was 98.3 mg/g at 20 °C. Adsorption isotherms of thiocyanate onto LDHC (LDHC dosage 2.0 g/L, T = 20 °C, initial pH 5.5).Figure optionsDownload high-quality image (65 K)Download as PowerPoint slideResearch highlights
► Previous research on adsorption of thiocyanate anions in aqueous solution by LDHC is limited.
► LDHC can be used as a new adsorbent for thiocyanate removal from aqueous solution because of its high adsorption capacity and fast adsorption rate.
► The adsorbed thiocyanates on LDHC can be desorbed in FeCl3 solution and the regenerated LDHC can be used repeatedly in adsorption-regeneration cycles.