Laterite clay-based geopolymer as a potential adsorbent for the heavy metals removal from aqueous solutions

This study is focused on the investigation of low iron lateritic clay-based geopolymer as a potential adsorbent for the higher uptake of Ni(II) and Co(II) ions from aqueous solutions. BET analysis revealed that the sieved geopolymer sample (SGS) was characterized by 17.441 m(2)/g of surface area, 0.005 cm(3)/g of pore volume, and 13.549A degrees of pore diameter. SEM investigation confirmed the presence of pores and cavities onto the surface of SGS. XRD analysis showed that the geopolymer is semi-crystalline in nature. It was found that the adsorption ability of SGS remained 520 mg/g for Ni(II) ions and 500 mg/g for Co(II) ions when 0.5 Msolutions were stirred with SGS for 60 min. The temperature and pH of the solution were maintained at 60 degrees C and 7.0, respectively. The adsorption data of both heavy metal (HM) ions fitted best in the pseudo-second-order kinetic model. The low activation energy value i.e. 2.507 kJ/mol for Ni(II) ions and 2.286 kJ/mol for Co(II) ions confirmed adsorption is physisorption. Adsorption data were tested with Langmuir and Freundlich models, the data showed comparatively better fitting in the Freundlich model. The greater value of monolayer adsorption capacity (Xm) for Ni(II) ions was found 1.77 x 10(-2) mol/g while for Co(II) ions it remained 1.69 x 10(-2) mol/g confirming the better interaction of metal ions with the adsorbent surface. Negative values of Delta G degrees confirmed the spontaneity of the process while the positive value of Delta S degrees showed the randomness of adsorbate particles. The positive value of Delta H degrees showed that the adsorption process remained endothermic for both HM ions. The experimental results confirmed the ability of laterite clay-based geopolymer for better removal of HM ions