Conversion of grass waste into activated carbon via pyrolysis assisted H3PO4 and KOH activation for methylene blue dye removal / Nur Muhammad Mohamad Zaki

Dye contamination in wastewater is one of the major sources which can cause water pollution and human health problem. Grass (Imperata cylindrical) (GIC) well knows as “Lalang” are agricultural wastes largely available in Malaysia, and it was disposed without non-economically values. In this study, GIC was utilized as a low-cost adsorbent, in order to prepare activated carbon by pyrolysis using phosphoric acid (H3PO4) and photassium hydroxide (KOH) activation method for adsorptive removal of methylene blue, a toxic dye from aqueous solution. The physical properties of the prepared raw grass cutting (RGC), modified grass cutting activated carbon acid (MGCACA), and modified grass cutting activated carbon base (MGCACB) were calculated through bulk density, iodine test, ash content, and moisture content. The characterization of RGC, MGCACA, and MGCACB were carried out using Elemental analyzer (CHNS-O), Brunauer-Emmet-Teller (BET) surface area, Scanning Electron Microscope (SEM), Fourier Transform Infra-Red Spectrometer (FTIR) and Point of Zero Charge (pHpzc) method. Batch adsorption experiments were performed to evaluate the effect of the adsorbent dosage (0.02 – 0.14 g), pH solution (3 – 11), initial concentration (50 – 300 mg/L), and contact time (50 – 450 min) on the adsorption of the methylene blue dye. The result showed that the efficiency methylene blue removal was highest at dosage (0.04 g and 0.08 g) for MGCACA and MGCACB under adjusted pH (7) for MGCACA and pH (6.8) MGCACB respectively. Validation method from BBD-RSM model was prove that the efficiency methylene blue was highest at the similar condition with batch adsorption study. The Langmuir model describes the adsorption behavior at equilibrium. The maximum adsorption capacities of MGCACB (287.92 mg/g) are higher than MGCACA (268.32 mg/g).