Potential of using jackfruit peel (Artocarpus heterophyllus) as green solution for removal of copper (II) and zinc (II) from aqueous solution: Adsorption kinetics, isotherm and thermodynamic studies

Adsorbent from agricultural waste has become a popular alternative method for heavy metal removal from aqueous solutions. The purpose of this study was to look into the feasibility of employing jackfruit peel (JP) (Artocarpus heterophyllus), a solid waste that is abundant in Malaysia, for the adsorption of Cu (II) and Zn (II) from an aqueous solution. In this work, jackfruit peels were investigated as an adsorbent with no chemical modification (JP), acidified (HJP), and base modified (NaJP) for Cu(II) and Zn(II) removal from aqueous solution by using batch-adsorption modes. Spectroscopic and electron microscopic methods were used to analyze the presence of surface functional groups such as -COOH and -OH and the morphologies of the adsorbent. Adsorption investigations were carried out by adjusting adsorbent dosage (0.10-0.50 g), solution pH (3-8), initial metal ion concentrations (20-250 mg/L), temperature (298-328 K), and contact time (0-360 min). Sorption equilibrium is quickly reached within 60 min, with a higher percentage of Cu(II) and Zn(II) removal for NaJP. Regarding the effect of initial concentration on JP, the maximum adsorption for Cu(II) and Zn(II) is at 50 mg/L and 30 mg/L, respectively. Meanwhile, for HJP, the maximum adsorption for Cu(II) and Zn(II) is at 230 mg/L and 30 mg/L, respectively. For NaJP, the maximum adsorption for Cu(II) and Zn(II) is at 20 mg/L. The pseudo-second-order model best characterized the kinetic data for both metal ions using JP, HJP, and NaJP. The experimental findings fit well with the Langmuir model in explaining the adsorption process, dominated by electrostatic interaction between the adsorbent and adsorbates, showing monolayer adsorption at the binding sites on the adsorbent's surface. It was proven that with the increase of adsorbent dosage, the percent of heavy metals removal was increased due to the increasing adsorption capability of the adsorbent. In conclusion, our findings show that jackfruit peel has the potential to remove Cu(II) and Zn(II) from an aqueous solution. The adsorption process for Cu(II) and Zn(II) was favourable in acidic conditions. Under the experimental conditions, the adsorption of Cu(II) and Zn(II) onto the surface of JP, HJP, and NaJP was exothermic and non-spontaneous. The results showed that the jackfruit peel, a waste material, has a high potential as an adsorbent for removing harmful metals such as copper and zinc from water.