Phosphate Adsorption using KOH Activated Coal Bottom Ash

: Research on phosphate adsorption using activated KOH coal bottom ash has been carried out. This study aims to assess the utilization of bottom ash as an adsorbent to adsorb phosphate ions from water bodies. Research starts from the activation process for 5 hours with 3 M NaOH solution. Then the pre-activated and post-activated bottom ash are characterized using Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS). Based on the results of the characterization with SEM-EDS, the surface of pre-activated bottom ash surfaces seems smooth because they are still covered by impurity metals such as Fe, Ti and Mg. After activation, bottom ash surfaces become rough because impurities such as Fe, Ti, and Mg are lost and thus the pores are opened. The bottom ash then was applied to absorb phosphate ions with variations of particle size (50-70 mesh, 70-110 mesh, and 110-140 mesh) and dosage of adsorbent (1, 2, and 3 g) and were contacted for 60 minutes to 1000 ml phosphate solute of concentration 10 mg/l. Remaining phosphate ions concentration in solute after adsorption are analyzed using UV-vis spectrophotometer. Best adsorption of phosphate ions with 74.8% efficiency was obtained at particle size of 110-140 mesh and dosage adsorbent of 3 g. The highest adsorption capacity (7.02 mg / g) was obtained with dosage of 1 g adsorbent. Freundlich and Langmuir's models were used to describe the phosphate ion adsorption by KOH activated bottom ash isotherm. Based on the data obtained, the suitable model for this study is Freundlich model with a value of R 2 = 0.9721.