Department of Chemical Sciences

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Browsing Department of Chemical Sciences by Subject "Adsorbent"

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    Adsorption of Lead and Cadmium Ions from Aqueous Solutions by Tripolyphosphate-Impregnated Kaolinite Clay
    (Elsevier, 2006-06) Unuabonah, Emmanuel
    The pretreatment of Kaolinite clay with tripolyphosphate (TPP) increased the cation exchange capacity (CEC) of Kaolinite clay from 13.45 meq/100 g to 128.7 meq/100 g. The equilibrium adsorption capacity of TPP–Kaolinite clay for Pb2+ and Cd2+ was 126.58 mg/g and 113.64 mg/g, respectively. The presence of Na- and Ca-electrolytes and with increase in their concentrations reduced the selectivity of TPP–Kaolinite clay for Pb2+ than Cd2+. TPP–Kaolinite clay showed higher selectivity for Pb2+ in the presence of these electrolytes and at all concentrations of these electrolytes used for the study. Binary mixtures of Pb2+ and Cd2+ in various concentrations caused a decrease in the adsorption capacity of TPP–Kaolinite for either metal ion. However, this may have caused the adsorption of Cd2+ onto high energy sites on the surface of the TPP–Kaolinite clay. Non-linear Chi-square model analysis of adsorption data using Langmuir, Langmuir–Freudlich, Freudlich, Toth and Temkin isotherms reveals that the adsorption of Pb2+ and Cd2+ by TPP–Kaolinite clay were best described by the Toth and Freudlich isotherms, respectively. At low concentrations (≤500 mg/L) the adsorption of these metal ions showed better fits to the five models with Langmuir–Freudlich and Freudlich isotherms giving the best fits for Pb2+ and Cd2+, respectively.
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    Disinfection of Water with New Chitosan-modified Hybrid Clay Composite Adsorbent
    (Elsevier, 2017-08-15) Omorogie, Martins
    Hybrid clay composites were prepared from Kaolinite clay and Carica papaya seeds via modification with chitosan, Alum, NaOH, and ZnCl2 in different ratios, using solvothermal and surface modification techniques. Several composite adsorbents were prepared, and the most efficient of them for the removal of gram negative enteric bacteria was the hybrid clay composite that was surface-modified with chitosan, Ch-nHYCA1:5 (Chitosan: nHYCA = 1:5). This composite adsorbent had a maximum adsorption removal value of 4.07 × 106 cfu/mL for V. cholerae after 120 min, 1.95 × 106 cfu/mL for E. coli after ∼180 min and 3.25 × 106 cfu/mL for S. typhi after 270 min. The Brouers-Sotolongo model was found to better predict the maximum adsorption capacity (qmax) of Ch-nHYCA1:5 composite adsorbent for the removal of E. coli with a qmax of 103.07 mg/g (7.93 × 107 cfu/mL) and V. cholerae with a qmax of 154.18 mg/g (1.19 × 108 cfu/mL) while the Sips model best described S. typhi adsorption by Ch-nHYCA1:5 composite with an estimated qmax of 83.65 mg/g (6.43 × 107 cfu/mL). These efficiencies do far exceed the alert/action levels of ca. 500 cfu/mL in drinking water for these bacteria. The simplicity of the composite preparation process and the availability of raw materials used for its preparation underscore the potential of this low-cost chitosanmodified composite adsorbent (Ch nHYCA1:5) for water treatment.
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    Unravelling the Effect of Crystal Dislocation Density and Microstrain of Titanium Dioxide Nanoparticles on Tetracycline Removal Performance
    (Elsevier, 2021-08-01) Omorogie, Martins
    New approaches are being developed to improve water purification using semiconductor nanomaterials to meet the 6th Sustainable Development Goal (SDG #6) of the United Nations (UN) on water sanitation. The pollutant removal performance of TiO2 nanoparticles is widely known to depend on its surface area/functionalisation. To unravel other intrinsic properties limiting its performance, a commercial Degussa P25 TiO2 was annealed at different temperatures, 450 °C and 600 °C, designated TiO2@450 °C and TiO2@600 °C, respectively. The scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), Brunauer-Emmett-Teller (BET), and electron diffraction spectroscopy (EDS) were employed to investigate the morphology, crystallinity, surface area, and bulk chemical composition, respectively of the as-annealed TiO2samples. While TiO2@450 °C samples displayed higher BET surface area and more oxygen content, TiO2@600 °C showed higher crystal dislocation and microstrains. Experimental results show better TC adsorption performance using TiO2@600 °C, attributed to its higher dislocation density and microstrains compared to TiO2@450 °C. Thus, more TC molecules are proposed to be adsorbed on the TiO2@600 °C due to their relatively higher defects. To examine the controlling mechanism of the TC adsorption process, the intra-particle diffusion model reveals TiO2@450 °C to possess 85 times the boundary layer of TiO2@600 °C, which limit diffusion in the former.