The possibility of using Albizia saman pod activated carbon (ASPAC) as an adsorbent in fixed down flow adsorption columns to remove Cd (II) from wastewater was investigated for the purpose of converting the waste to a valuable product. The effects of impregnation ratio, particle size, carbon height, pressure head and initial cadmium Cd (II) concentration on the adsorption of Cd (II) from wastewater were investigated. The obtained adsorption data from the experiment was then fitted into the Hutchin's bed depth service time (BDST) model to study the columns performance at 15% and 90% breakthrough concentrations. The BDST model constants were determined. An optimal pressure head of 5 cm, impregnation ratio of 1:6, packing height of 3.5 cm, particle size of 75 µm and initial Cd (II) concentration of 0.029 mg/L were found to be the most effective combination, which removed 100 % of the Cd (II) within a service time of 14 hrs. There was a gradual decrease in the percentage of adsorbed Cd (II) with time; the percentage adsorbed became zero at 44, 56 and 86 hours respectively for 2.5 cm, 3 cm and 3.5 cm carbon heights. The breakthrough curves for Cd (II) adsorption maintained the characteristic S-curve for most dynamic studies. Chisquared test performed on the developed BDST models revealed the goodness of fit of the models for the prediction of the columns performance at all breakthrough concentrations investigated. The use of ASPAC as adsorbent for the removal of Cd (II) from wastewater in adsorption columns is therefore recommended.

Activated carbons were produced from a local variety of mango seed by carbonizing the inner seed before activation with ZnCl 2 using an impregnation ratio of 1:4. Laboratory batch studies were conducted in order to generate data for kinetic and equilibrium modelling of adsorption of colour by the produced mango seed endocarp activated carbon (MSEAC) for the purpose of determining the mechanism and rate controlling steps of the adsorption process. Langmuir, Freundlich and Tempkin Isotherms were adopted. While the kinetic models used were pseudo first order kinetic, pseudo second order kinetic, Intra-particle diffusion and Elovich models. The pseudo second order model gave the highest coefficient of determination (R 2) of 0.999 (indicating goodness of fit) compared to other kinetic models tested. This suggests that chemisorption is the rate-limiting step in this biosorption system. Langmuir isotherm fitted experimental data better compared with the other tested models(R 2 =0.9987), implying that the adsorption process is based on a monolayer adsorption. Chi-squared test performed on all the models confirmed the goodness of fit of the generated data to the Langmuir and pseudo-second order over the other isotherm and kinetic models because they had the least caculated Chi-squared (χ 2 Cal) values of 5.2 and 3.2 respectively. It was recommended that these two models are reliable tools for predicting the mechanism and rate of adsorption of colour from textile wastewater by the produced MSEAC.

Activated carbon was prepared from the pods of Albizia saman for the purpose of converting the waste to wealth. The pods were thoroughly washed with water to remove any dirt, air- dried and cut into sizes of 2-4 cm. The prepared pods were then carbonised in a muffle furnace at temperatures of 4000C, 5000C, 6000C ,7000C and 8000C for 30 minutes. The same procedure was repeated for 60, 90, 120 and 150 minutes respectively. Activation was done using impregnationratios of 1:12, 1:6, 1:4, 1:3, and 1:2 respectively of ZnCl2 to carbonised Albizia saman pods by weight. The activated carbon was then dried in an oven at 1050C before crushing for sieve analysis. The following properties of the produced Albizia saman pod activated carbon (ASPAC) were determined: bulk density, carbon yield, surface area and ash, volatile matter and moisture contents. The highest surface area of 1479.29 m2/g was obtained at the optimum impregnation ratio, carbonization time and temperature of 1:6, 60 minutes and 5000C respectively. It was recommended that activated carbon should be prepared from Albizia saman pod with high potential for adsorption of pollutants given the high surface area obtained.Keywords: Albizia saman pod, activated carbon, carbonization, temperature, surface area