Adsorption of Humic Acid onto Jordanian Kaolinite Clay: Effects of Humic Acid Concentration, pH, and Temperature

Kaolinite clay has low cation exchange capacity and small surface area; it has rarely been used as adsorbent. As well as, green, low cost and efficient adsorbent is desired. Modification of kaolinite is necessary to improve its adsorption capacity. Jordanian kaolinite has been modified by humic acid (HA) through batch adsorption mode. Two types of HA were used; one was commercial (FHA) and the other was natural (KTD). The effect of HA concentration, pH and temperature of solution were considered. HA adsorption becomes higher at low concentration, decreases with increasing pH, and it increased with solution temperature. Modified Jordanian kaolinite clay was characterized by different techniques: FTIR, TGA, SEM connected to EDS and porosimetry analysis by Gas Adsorption Isotherm and Mercury Porosimetry. The modified kaolinite showed good and strong interaction with HA, enhancement in its surface and charge structure, and increasing in the average pore radius. Therefore, increases in its reactivity and adsorption sites especially towards heavy metal ions. Moreover, FHA– kaolinite clay showed better adsorption characteristics than KTD– kaolinite clay.