Optimization of Heavy Metals Adsorption using Modified Charcoals from Coconut and Palm Kernel Shells via Response Surface Methodology

Nur Rafikah, Rosli (2019) Optimization of Heavy Metals Adsorption using Modified Charcoals from Coconut and Palm Kernel Shells via Response Surface Methodology. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Heavy metals contamination in water bodies is a very common environmental issue especially in industrial area. There are many ways for removing heavy metals from water body but most of them are either expensive, or inefficient. Adsorption is a preferred technology for removal of heavy metals especially when the adsorbent are made of cheap precursor. In this study, coconut shell charcoal and palm kernel shell charcoal were converted into modified charcoal via acid-base modification. The charcoals were being soaked in 20% NaOH for 2 h, dried for 24 h oven and then followed by adding of 5M HCl to remove salt prior to washing with deionized water. Batch experiments were performed to investigate the adsorption capacity of palm kernel shell and coconut shell charcoal in removing heavy metals namely chromium, nickel and copper from aqueous solution. In order to achieved highest adsorption capacity of palm kernel shell charcoal and coconut shell charcoal Response Surface Methodology (RSM) was applied. A Central Composite Design (CCD) experiments were conducted involving three parameters which were pH of heavy metal solution, time contact and size of particles. All together 17 experiments were run for each heavy metals for each sample. Characterization of coconut shell charcoal (CSC) and palm kernel shell charcoal (PKSC) has been successfully performed by using CHN elemental analyzer, FTIR spectrometer, SEM analyzer, and BET analyzer. The modifications have successfully increased the surface area of CSC and PKSC from 185.712 m2/g to 246.896 m2/g and from 112.934 m2/g to 149.670 m2/g for each sample respectively. The pore structure also seems to be bigger after the modifications process hence providing more area for the metal ions to attach to. The batch experiments study showed that MCSC and MPKSC exhibited better heavy metal removal efficiency compared to CSC and PKSC in most study namely initial concentrations and contact time. For isotherm study in CSC and MCSC, the results best described by the Langmuir isotherm meanwhile PKSC and MPKSC samples were best described by Frendlich isotherm. In kinetic study, all four samples was found out to fit the pseudo second order with high correlation coefficient (more than 0.95) indicating chemical adsorption occurs throughout the sorption process. From the CCD experiments, it was found out that, pH of metals solution and size of particles affect the removal efficiency. The right combination of these two dominant factors can give highest removal efficiency in removing heavy metals. However, it was envisaged that time contact does not really affect the removal efficiency. The findings of this research will provide new insights to remove heavy metals from wastewater system.

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