The effect of chemical activation on the adsorption of metals ions (Cr2+, Cu2+, Ni2+, Pb2+, Fe2+, and Zn2+) using waste Nigerian based bamboo, coconut shell, and palm kernel shell was investigated. The bamboo, coconut, and palm kernel shell were carbonized at 400°C–500°C and activated at 800°C using six activating agents. Chemical activation had significant effect on the iodine number and invariably increased the micropores and macropores of the activated carbons produced from bamboo, coconut, and palm kernel shell. It also affected the adsorption of metal ions and the type of carboneous material used for activation. The highest metal ions adsorbed were obtained from bamboo activated with HNO3. The cellulose nitrite formed during the activation of bamboo with HNO3 combined with high pore volume and low ash content of bamboo effectively create more reaction sites for adsorption of different metal ions. This shows that waste bamboo activated with HNO3 can effectively be used to remove metal ions from waste streams and in different metal recovery processes than activated carbon from coconut shell and palm kernel shell.
The increased concern by environmentalist and government on the effect of heavy metals and
Yan and Viraraghavan [
The results obtained from previous studies reviewed above showed that different carboneous materials have different reactivity to different activating agents. Bamboo, palm kernel, and coconut shell have been found to be good materials for production of activated carbon [
The following materials and apparatus were used for this work: waste Nigeria based bamboo, and waste coconut shell, waste palm kernel shell. Activating agents are hydrochloric acid, phosphoric acid, sulphuric acid, nitric acid, zinc-chloride, and sodium hydroxide. A pyrolytic reactor was used for carbonization with condenser. Other materials used are measuring cylinder, heating mantle, desiccators, crucibles, funnels, and filter papers. Two electronic weighing balance, Ohaus top loading balance (+0.01) was used to weigh the bamboo before pyrolysis, while a more sensitive electronic analytical weighing balance (+0.001, Adams AFP 360L) was used for another analysis, retort stand, thermocouple with temperature sensor, spatula, density bottle, crusher, sieves, measuring cylinders, moisture cans, and petri dish.
Known weight of waste coconut shell and waste palm kernel shell was cut into small sizes, washed, and dried. They were carbonized differently in a pyrolytic reactor at about 400–500°C for about two hours after which the charred products were allowed to cool to room temperature. The charred material was crushed using mortar and pistol and sieved.
The carbonised waste bamboo, palm kernel, and coconut shell were weighed separately and poured in different beakers containing known quantity of dilute hydrochloric acid, phosphoric acid, trioxonitrate (v) acid, tetraoxosulphate (vi) acid, zinc-chloride, and sodium hydroxide (H2SO4, HCL, ZnCl2, H3PO4, NaOH, and HNO3). The concentrations of the acid used were already determined before this study. The content of the beakers was thoroughly mixed until a paste of each was formed. The pastes of the samples were then transferred to crucibles and the crucibles were placed in a Muffle furnace and were heated at 800°C for two hours. The activated samples were then cooled at room temperature, washed with distilled water to a pH of 6-7, and dried in an oven at 105°C for three hours. The final products were sieved to same particle size kept in an air tight polyethylene bags, ready for use. Note that different concentrations (ranging from 0.025 M–0.5 M) of each activating agents were prepared and used to activate waste bamboo, palm kernel, and coconut shells before the adsorption of the metal ions.
The waste Nigerian based bamboo, waste coconut shell, and waste palm kernel shell used in this work were characterised (iodine number, Methylene blue number, density, etc.), using the ASTM methods as described in the work of Ademiluyi et al. [
Six metal ions (Cr2+, Cu2+, Ni2+, Pb2+, Fe2+, and Zn2+) frequently found in industrial and municipal wastewater were chosen for this study. All metal ions in solutions were made by dissolving a known quantity of each salt containing these metals in distilled water in the ratio 1 : 1000. 2 g of the activated carbons activated with the six activating agents was added separately to the six mixtures containing each metal ion in solution and stirred for 30 minutes, it was filtered with a filter paper to get the filtrate. The same procedure was carried out for others (Zn2+, Cr3+, Pb2+, Ni2+, and Fe2+).
The amount of metal ions in solution (i.e., Zn2+, Cr3+, Pb2+, Ni2, and Fe2+) was determined using conductometric method from the filtrate after adsorption using waste Nigerian based bamboo, waste coconut shell, and waste palm kernel shell. As described in the work of Banjonglaiad et al. [
The iodine number is the most fundamental parameter used in characterizing activated carbon. It is a measure of activity level and the micropore content of the activated carbon (higher number indicates higher degree of activation, [
Effect of chemical activation on the iodine number of activated carbon from waste bamboo, coconut, and palm kernel shell.
Similarly, in the work of Ramírez Zamora et al. [
Table
Characterization of activated carbon from bamboo, coconut, palm kernel, and other reference activated carbons.
S/N | Parameter | Unit | Locally made GAC | References activated carbon | ||
---|---|---|---|---|---|---|
Bamboo | Coconut | Palm kernel | ||||
1 | Bulk density | g/cm3 | 0.458 | 0.8086 | 0.8332 | 0.2–0.6 Long and Criscione [ |
2 | Methylene blue adsorptive capacity | mg/g | 941.325 | 46.30755 | 42.230 | 900–1100 Wikipedia [ |
3 | Iodine number | g of iodine/kg of C. | 1,197.45 | 559.8971 | 709.20 | 500–1200 Long and Criscione [ |
4 | Ash content | % | 2.760 | 0.98 | 6.435 | ≤8 Metcalf and Eddy [ |
5 | Pore volume | Cm3 | 0.4543 | 0.1777 | 0.1731 | 0.5–2.5 Long and Criscione [ |
Figure
Adsorption of metal ions before activation of local adsorbents and commercial activated carbon.
The effect of activation on the adsorption of lead ion (Pb++) using activated carbon from waste bamboo, palm kernel and coconut shell is presented in Figure
Effect of chemical activation on the adsorption of lead ion (Pb++) using waste bamboo, palm kernel shell, and coconut shell activated carbons.
The effect of chemical activation on the adsorption of iron II ions (Fe2+) using activated waste bamboo, palm kernel, and coconut shells is presented in Figure
Effect of chemical activation on the adsorption of Fe2+ ions using activated waste bamboo palm kernel and coconut shells carbons.
A look at Figures
Effect of chemical activation on the adsorption of Cr3+, Cu2+, Ni2+, and Zn2+ ions in solution using activated carbon from bamboo.
Figure
Adsorption of different metal ions using bamboo activated with HNO3 and commercial activated carbon.
The effect of chemical activation using different activating agents on the adsorption of heavy metals ions using activated carbons from waste materials such as bamboo, palm kernel shell, and coconut shell has been investigated. Chemical activation had a significant effect on the adsorption of metal ions and on the type of carboneous material used. The adsorption of metal ions using bamboo, coconut, and palm kernel activated with HNO3, H2SO4, and HCL was significantly higher than carbons activated with ZnCl2, NaOH, and H3PO4. The highest metal ion adsorbed was obtained from bamboo activated with HNO3. The cellulose nitrite formed during the activation of bamboo with HNO3 created more active reaction site for adsorption of different metal ions. This shows that waste bamboo activated with HNO3 can effectively be used to remove metal ions from waste streams and in different metal recovery processes than coconut and palm kernel.