Pollution of the aquatic environment by heavy metals has detrimental effects on living species. In this work, Nano-composite Adsorbents were developed using agricultural waste (i.e. Palm Kernel shell, Coconut shell and Bamboo stem). These agro-wastes were collected, dried separately and repeatedly crushed to a Nano-size. The characterization of these adsorbents were done separately using SEM and Zetasizer machines. The Adsorbents were activated with four different activating agents (0.1M H2SO4, 0.1M HCl, 0.1M NaOH and 0.1M KOH) named Adsorbent A, B, C and D respectively. The wastewater from Paint industry was collected from the point of discharge and analyzed using AAS machine to determine the heavy metals composition that was above the allowable limit. The results of three heavy metals selected were Cu = 2.006mg/L, Pb = 1.634mg/L and Ni = 0.785mg/L being higher than the standard admissible limit. Four adsorbents were used for the removal of the selected heavy metals (Cu, Ni and Pb) from Paint industrial wastewater to meet the standard limit. Adsorption application and performance evaluation of the four Adsorbents for the removal of copper, nickel and lead ions from paint wastewater solution was carried out in a batch mode. Results from the characterization of the three agricultural wastes showed that Palm kernel shell had higher surface area of 1164m2/g. Optimum adsorption capacity of Adsorbents A, B, C and D were observed at pH 5 and 1 g/L dosage, while equilibrium adsorption conditions were generally noticed after 60 minutes of agitation at 100 rpm. The initial metal concentrations, pH of solution, contact time of adsorbate with the adsorbent, adsorbents dosage and functional groups on adsorbents were the major factors affecting the affinity of metals by all the Adsorbents. The maximum adsorption capacity of Adsorbent A (Cu = 1.607 mg/g, Pb = 0.802 mg/g, and Ni = 0.126 mg/g), Adsorbent B (Cu = 1.550 mg/g, Pb = 0.752 mg/g, and Ni = 0.105 mg/g), Adsorbent C (Cu = 1.013 mg/g, Pb = 0.512 mg/g, and Ni = 0.069 mg/g) and Adsorbent D (Cu = 1.030mg/g, Pb = 0.555 mg/g, and Ni = 0.065 mg/g) gave a trend of metals affinity for adsorbents as Cu>Pb>Ni. Langmuirâ€™s model was observed to be better in predicting the adsorption process than Freundlichâ€™s model.
Keywords: Nano-composite Adsorbents, characterizations, SEM, Zetasizer, AAS machine