Study on the performance of metakaolin based geopolymer for Mn(II) and Co(II) removal

The aim of this study is to remove heavy metals ions of Mn(II) and Co(II) from aqueous solutions by using metakaolin based geopolymer, a new potential low-cost alternative adsorbent material. The parameters of initial pH, adsorbent amount, time of contact and initial metal ion concentration on the metal removal performance were studied using a batch method at 30 °C. It was found that the Langmuir isotherm described the adsorption data very well and the maximum monolayer adsorption capacities were found to be 72.34 mg g−1 (1.32 × 10−3 mol g−1) and 69.23 mg g−1 (1.18 × 10−3 mol g−1) for Mn(II) and Co(II), respectively. The kinetic studies showed that adsorption of Mn(II) and Co(II) followed the pseudo-second-order kinetic model. Adsorption yield was found to be slightly sensitive to temperature and ionic strength and no pH adjustment was necessary to get high adsorption yield. High metal ion adsorption performance in both batch and continuous systems is an important indicative of geopolymer efficiency. Ion exchange appears to be an effective mechanism for the metal ion adsorption onto geopolymer. It is concluded that Mn(II) and Co(II) ions are efficiently removed from aqueous solutions by metakaolin based geopolymer which could be employed as a low-cost and excellent alternative for wastewater treatment.