Clay-Rice Husk Ash based Geopolymers for Remediationof Pb (II) and Cd (II) from Wastewater

Abstract

Industrialization and technological advancements have led tothegeneration ofnumerouspollutantssuch asheavy metals into the aquatic ecosystem. These toxiccompounds are extremely dangerous to humanhealthand the environment due totheir non-biodegradability, severe toxicity, ability toaccumulateand contaminateground and surface waters. Subsequently, pursuance of sustainable materials andtechnologies for better attainment of environmental sustainability is critical. Thisstudy reportsthesynthesis of geopolymers GP-1, GP-2 and GP-3fromdifferentclays. Geopolymers were hydrothermally synthesized using clay and rice huskswaste as an alumina and silica source respectively. The geopolymers werecharacterized using Fourier transform-infra red, energy dispersive spectrometry,X-ray diffraction and scanning electron microscope. Batch and gravitationalcolumn experiments using Pb (II) and Cd (II) ions were carried out. Increasedmetal ion uptake was recorded with raised Si/Al ratio of the adsorbents. The meanpercentage uptake of 90.23 ± 0.4 and 89.63 ± 0.18 of Pb (II) and Cd (II) wereachieved at pH of 4.0 and 5.0 respectively using GP-3.Langmuir, Freundlich andmodified Langmuir Freundlich isotherms were used in equilibrium studies.Datafor adsorption of Pb (II) and Cd (II) fitted best inthemodified LangmuirFreundlich model.The highest adsorption capacities of Pb (II) and Cd (II) were209.9 and 136.2 mg/g respectively, attained using GP-3.Based on the resultsobtained, geopolymers produced from common clay and rice husk wastedisplayed promising potentialsin theremoval of heavy metal ions from theaqueous phase. Considering the availability of raw materials forgeopolymerization and the high metal ions uptake capacities of geopolymers,they can also be used as adsorbents for removal of heavy metals in industrialwastewater.Keywords:Adsorption;Characterized;Geopolymers;Isotherm; Wastewater.