Removal of copper (II) ions by phosphoric acid and iminodiacetic acid modified kenaf fiber

Kenaf fiber can be chemically modified to enhancing their metal-binding ability by introducing new functional groups. The aim of this research was to prepare kenaf fiber (K) modified with phosphoric (K-PA) and iminodiacetic acid (K-IDA). The use of modified fiber for the removal of heavy metals which is Cu2+ is reported. The adsorbents is chemically modified with PA and IDA and in order to obtain the additional of functional group and the morphology in modified kenaf fiber, several characterization instruments were used such as Fourier Transform Infrared Analysis (FTIR), Elemental Analysis (CHNS), Scanning Electron Microscopy (SEM), Surface Area and Porosity Analysis (BET). K-PA and K-IDA show an increase in adsorption capacity of Cu2+when compared to the untreated fiber. The adsorption capacity of Cu2+ is in the following order: K-PA < K-IDA. Under the optimum conditions of pH 5 and a minimum of 0.1 g of adsorbent, K-PA and K-IDA adsorbsCu2+at amounts corresponding to the maximum adsorption efficiencies with percentages of removal of 90% and 99%, respectively. The adsorption capacity increased with increasing initial Cu2+ concentrations and followed the Langmuir model and pseudo second order kinetic mechanism for K-PA and K-IDA. The maximum sorption capacities as calculated from the Langmuir isotherm for K-PA and K-IDA were 64.52 and 91.74 mg g-1 respectively. Higher adsorption capacity at higher temperature indicates that the Cu2+ sorption process is endothermic for all adsorbents. The free energy changes, G for the sorption by K-IDA was negative indicating that the sorption process is spontaneous, while vice versa for K-PA. In the selectivity study, Kd for Cu2+ is higher than other heavy metal ions for K-IDA while Kd for Pb2+ is the highest value for K-PA. The foreign ion study showed that the sorption of Cu2+ was significantly affected by the presence of Cr3+, Pb2+ and Zn2+ except while with K-IDA. For the desorption study, it was observed the highest percentage desorption of Cu2+ towards K-PA and K-IDA was 95.41%, 99.46% respectively by using 1 M hydrochloric acid. For the reusability study, adsorption capacity for K-IDA did not vary until 4th cycle. Nevertheless, the adsorption capacity for K-PA suddenly decreases after the 2nd cycle. Both modified kenaf fibers, K-PA and K-IDA were found to be effective for the removal of Cu2+ in real wastewater samples obtained from electroplating waste and wood treatment industries. In conclusion, the modified kenaf fiber has potential to be used as effective heavy metal adsorbent for water treatment.

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