Physical and chemical modified forms of palm shell: preparation, characterization and preliminary assessment as adsorbents

Abstract

A series of adsorbents were obtained from palm shell (Borassus flabellifer) powder (PSP) which is an agro-waste. PSP was carbonized using sulphuric acid (APSP). APSP was subjected to the following modification procedures: activation to different temperatures (3AAC, 6AAC, 7AAC and 9AAC); activation with steam and persulfate (SAPSP and PAPSP) at 140 °C. Further the effect of modification of PSP, APSP, SAPSP and PAPSP using formaldehyde (MPSP, MAPSP, MSAPSP and MPAPSP) was also investigated. The materials were characterized using SEM, FTIR, TGA and XRD. N2 adsorption isotherms, DR equation and BJH methods were used to characterize the pore structure of the prepared carbons. The iodine value for APSP, SAPSP and PAPSP were found to be 342.5, 199.8, 299.7 mg/g respectively. They were also found to have large pores as well as chelating functional groups indicating their potential adsorption capacity. The carbon 9AAC was found to have high BET surface area of 834 m2/g and a pore volume of 0.4474 cm3/g with predominant micro-pores. Selectivity coefficients for different mixtures containing mercury, copper, zinc and cadmium have been determined for PSP, MPSP, APSP, SAPSP, PAPSP and 9AAC. Though PSP, APSP, SAPSP, PAPSP and MPSP did not have appreciable surface area, they showed encouraging results for adsorption of heavy metals indicating the potential use of palm shell as an economic precursor in the activated carbon preparation process.