Faculty of Science

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Browsing Faculty of Science by Subject "Equilibrium"

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    Adsorption of Cadmium Ions on Geopolymers Derived from Ordinary Clay and Rice Husk Ash
    (International Journal of Materials and Chemistry, 2018-10-07) Maingi, Francis M.; Mbuvi, H. M.; Ng’ang’a, M. M.; Mwangi, H.
    The presence of heavy metals in water is of growing concern. One crucial global strain is the existing disparity in water distribution resulting into millions of people lacking access to safe clean water. This is exasperated by the looming climate change and increased pollution impendence posed by industrialization and population growth. Consequently, pursuance of sustainable materials and technologies for wastewater remediation is critical. Adoption of adsorbents for water treatment is desirable due to their simplicity and cheap materials involved. Geopolymers are prepared hydrothermally using alumina and silica gleaned from clay and rice husks waste materials respectively. These materials are locally attainable and environmentally benign. This work reports synthesis of geopolymers GP-1, GP-2 and GP-3 prepared using clays from three different regions. The XRD diffraction patterns obtained revealed the presence of quartz (SiO2), albite (NaAlSi3O8), vermiculite (Mg,Fe,Al)3((Al,Si)4O10)(OH)2.4H2O), microcline (KAlSi3O8), analcime (NaAlSi2O6•H2O) and natrite (Na2CO3) among other crystalline phases. The initial adsorption rates were found to increase as the Si/Al ratio of the geopolymers increased. The adsorption rates were found to fit into the second order kinetic model. This implies that Cd (II) ions adsorb on geopolymer adsorbents through chemisorption.
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    Thermodynamic, Kinetic and Equilibrium Studies of Pb (II) Ions Adsorption Using Ordinary Clay/Rice Husk Ash Based Geopolymers
    (IOSR Journal of Applied Chemistry, 2018-08-08) Maingi, Francis M.; Ng’ang’a, M. M.; Mwangi, H.; Mbuvi, H. M.; Abdulhameed, Adamu
    One key global challenge is the existing disparity in water distribution resulting to millions of people lacking access to safe clean water. It is currently assessed that 1.1 billion individuals on the planet lacks access to improved quality water supplies. This is aggravated by the looming climate change and increased pollution threats posed by industrialization and population growth. Use of adsorbents for water treatment is preferable due to simplicity of the technique and cheap materials involved. Geopolymers can be easily synthesized hydrothermally using alumina and silica and possess amorphous surface for use as adsorbents. Clay minerals have been reported to contain alumina and silica and previous research show that rice husk ash as well contain substantial amounts of silica. Geopolymers can be easily synthesized hydrothermally using alumina and silica and possess amorphous surface that is useful for adsorption. Hence this work reports information on adsorption of Pb (II) using geopolymers GP-1, GP-2 and GP-3 synthesized with SiO2/Al2O3 ratios of 4.16, 4.18 and 8.29 respectively. Adsorption of metal ions was found to increase from 70.54%± 0.43 to 90.23% ± 0.04 with increase in Si/Al ratio from 4.16 to 8.29 in geopolymers. Equilibrium studies unveiled that experimental data for adsorption of Pb (II) ions best fitted in modified Langmuir Freundlich model. The adsorption capacities of 27.0, 79.58 and 209.9mg/g were obtained for GP-1, GP-2 and GP-3 respectively. Adsorption thermodynamics showed the process corresponded on spontaneous physiosorption activated by increase in temperature. Kinetic study on adsorption of Pb (II) ions onto clay based geopolymers was a Pseudo second order. This information may facilitate the development of optimized procedures for wastewater treatment, thus providing an alternative solution to environmental menace caused by heavy metal pollutants.