A Study of Nanoscale Zeolitic Imidazole Framework-8 in Removal of Humic Acid from Wastewater by Adsorption

Wastewater contains natural organic matter which consists of various kinds of acids such as humic acid, amino acid, fulvic acid, etc. Humic acid can easily dissolve in water and impart brownish color thus this very compound draws our attention. Humic acid has other problems such as converting into toxic compounds during chlorination and increasing the concentration of manganese and iron in groundwater. Therefore, humic acid causes health issues for drinking water and needs to be removed. To remove the humic acid, we developed an efficient adsorbent known as Zeolitic imidazole framework-8 (ZIF-8). ZIF-8 is mainly selected as it has a very high surface area and high stability in the aqueous medium. Regeneration of ZIF-8 can be done by using an easy ethanol-washing process and it can be reused too for humic acid adsorption. Hence, ZIF-8 is a stable and efficient adsorbent for the removal of humic acid from water owing to these factors. The characterization of ZIF-8 was done using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Factors that affect the adsorption of humic acid were observed, including temperature, mixing time, solid-to-liquid ratio, and pH. The removal efficiency increased from 27 to 83% as we increased the S/L ratio from 0.5 to 2.5. The removal efficiency is also increased with time and decreased with temperature as expected.