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A B S T R A C TRecent studies have shown that kaolinite clay modified with biosorbents are promising low cost adsorbents for the removal of metals from aqueous solution because the resultant composites have higher adsorption capacities, and hence a better aqueous metal ions removal efficiencies. However, some clay properties suggest that not all such modifications enhance adsorption capacity. In this study, bentonite (BEN) clay was calcined after modification with Carica papaya seeds or pine cone to obtain C. papaya-modified bentonite (CPB) and pine cone-modified bentonite (PCB). The efficiencies of these adsorbents for the removal of Pb(II), Cu(II) and Cd(II) ions from aqueous solutions were studied as a function of pH, time, sorbate concentration and temperature. X-ray diffraction results showed that CPB and PCB had lattice structure as BEN, but reductions in the surface areas of CPB and PCB were observed. Adsorption results showed that pH did not significantly affect removal of aqueous metal ions between pH 3 and 7. The adsorption fitted pseudo-second order (r 2 ! 0.966) and intra-particle diffusion models and indicated mainly surface phenomena involving sharing of electrons between the adsorbent surfaces and the metal ion species. Unlike Cu(II) and Cd(II), Pb(II) adsorption reduced in CPB and PCB indicating that not all calcined biomass-clay composites have enhanced aqueous metal adsorption efficiency. However, undesired properties such as adsorbent bleeding were removed and mechanical strength enhanced while easier separation of the adsorbents from solution as compared to the raw bentonite was observed.

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Environmental remediation has been a strategy employed by scientists to combat water pollution problems that have led to the scarcity of potable water. Hence, in this study, Terminalia ivorensis seed waste (TISW) was explored for the removal of Congo Red, Methylene Blue, Cadmium and Lead from aqueous solutions. Some experimental variables such as pH, biosorbent dose, initial solute ion concentration, agitation time and temperature were optimised. The surface microstructures of TISW were studied using proximate analysis, bulk density, specific surface area, pH of Point of Zero Charge, Fourier Transform Infra Red Spectroscopy, Thermogravimetric/Differential Thermal Analysis, Scanning Electron Microscopy and Energy Dispersive Analysis of X-ray. The maximum Langmuir monolayer saturation adsorption capacity, q max L , was obtained as 175.44 mg/g for the removal of Methylene Blue by TISW. Also, the q max L for CR, Cd(II) ion and Pb(II) ion were 85.47, 12.58 and 52.97 mg/g, respectively. Also, the pseudo-first-order constant, k 1 , and pseudo-second-order rate constant, k 2 , are 0.008-0.026 min -1 and 0.012-0.417 mg g -1 min -1 , respectively. Hence, TISW is recommended as a good adsorbent for the removal of both toxic industrial dyes and toxic metal ions from polluted water.

Methylene Blue (MB) was adsorbed from aqueous solution using Baobab (Adansonia digitata L.) fruit pod and its goethite modified form. Adsorbents were characterized using Fourier Transform-Infra Red (FTIR) spectroscopy and Scanning Electron Microscopy (SEM). Batch experiments were conducted at room temperature (26.8 °C) and the adsorption data were fitted using Langmuir, Freundlich, Temkin and Dubinin- Radushkevich isotherms. Also, kinetic data was fitted using Pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion models. Goethite modified baobab (GMB) appeared to have a coarse microporous surface with smoother surface and larger pore volumes compared to unmodified baobab (UB). The –C=O band was observed at 1631 and 1636 cm-1 for UB and GMB. The –OH band was observed at 3447.00 cm-1 and 3442 cm-1 for UB andGMB respectively. Langmuir model was suitable for describing the adsorption data of UB with R2 of 0.9293 while Temkin model was best for fitting adsorption data of MB on GMB with R2 of 0.9691. However, maximum adsorption capacity was obtained with Freundlich adsorption isotherm (15.4253 and 43.1301 mg/g for UB and GMB respectively). The maximum biosorption were 8.98 mg/g and 9.86 mg/g for UB and GMB respectively at pH 10. Pseudo-second-order kinetic model best fitted the kinetic data with R2 values of 0.9968 and 0.9993 for UB and GMB, ΔHo values were 83.123 KJ/mol and 361.094 KJ/mol for UB and GMB, while ΔSo values were 3.084 J/mol/ K and 1.765 J/mol/K for UB and GMB respectively. GMB adsorbed more of MB than UB and the process was endothermic. Keywords: Biosorption, Goethite, Baobab, Isotherms, Methylene blue.