Magnesium silicate impregnation on palm-shell activated carbon powder for enhanced heavy metal adsorption / Choong Choe Earn

• Main Author: Choong , Choe Earn
• Format: Thesis
• Published: 2018
• Subjects: TA Engineering (General). Civil engineering (General)
• Online Access: http://studentsrepo.um.edu.my/9700/1/Choong_Choe_Earn.pdf; http://studentsrepo.um.edu.my/9700/2/Choong_Choe_Earn_%2D_Thesis.pdf; http://studentsrepo.um.edu.my/9700/
• Institution: Universiti Malaya

In this work, palm-shell waste powder activated carbon (PPAC) coated by magnesium silicate (PPAC-MS) were successfully synthesized by the impregnation of magnesium silicate (MgSiO3) using economical material (silicon dioxide powder) via mild hydrothermal approach under one-pot synthesis for the first time. Surprisingly, PPACMS exhibited a homogeneous thin plate mesh-like structure, as well as meso- and macro-pores with a high surface area of 772.1 m2 g-1. Different impregnation ratios of MgSiO3 onto PPAC were tested from 0% to 300%. High amounts of MgSiO3 led to high Cu (II) adsorption capacity. A ratio of 1:1, designated as PPAC-MS 100, was considered optimum because of its chemical stability in solution. The maximum adsorption capacity of PPAC-MS 100 for Cu (II) obtained by isotherm experiments was 369 mg g-1. Kinetic adsorption data fitted to pseudo-second-order revealed chemisorption. Increasing ionic strength reduced Cu (II) adsorption capacity because of the competition effect between Na+ and Cu2+. Three times of regeneration studies were also conducted for Cu (II) removal. In addition, PPAC-MS 100 showed sufficient adsorption capacity on removal Zn (II), Al (III), Fe (II), Mn (II), and As (V) with the adsorption capacity of 373 mg g-1, 244 mg g-1, 234 mg g-1, 562 mg g-1, 191 mg g-1, respectively. As an effective adsorbent, PPAC-MS 100 simultaneously removes Bisphenol A (BPA) and Pb (II) in single and binary mode. Due to its specific morphological characteristics, PPAC-MS 100 had adsorption capacities of Pb (II) as high as 419.9 mg g-1 and 408.8 mg g-1 in single mode and binary mode based on Freudliuch isotherm model while those for BPA by PPAC-MS were 168.4 mg g-1 and 254.7 mg g-1 for single mode and binary modes corresponding to Langmuir isotherm model. Experiment results also indicated that the synergistic removal of BPA occurred because the precipitation process of Pb (II) leads to the co-precipitation of BPA with Pb(OH)2 compound. PPAC-MS showed a good reusability for 5 regeneration cycles using Mg (II) solution followed by thermal treatment. PPAC-MS is characterized by Fourier Transformed Infrareds (FTIR), nitrogen adsorption/desorption analysis, X-Ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Field Emission Scanning Electron Microscope (FESEM). Overall, PPAC-MS has a high potential in the treatment process for wastewater containing both toxic heavy metals and emerging pollutants due to its high sorption capacities and reusability, while remaining economical through the reuse of palm-shell waste materials.