Evaluation of Ultrasound-assisted Modified Fly Ash for Treatment of Acid Mine Drainage

Abstract

The aim of this chapter is to assess the suitability of utilizing fly ash (FA) and modified fly ash (MFA) in the treatment of acid mine drainage (AMD). The effects of various experi- mental conditions such as mixing speed, fly ash dosage, contact time, and pH on the efficiency of metal removal from AMD was studied in batch experiments. For modifica- tion of FA, ultrasound (US) process was conducted at low frequency (20 kHz) to activate surface area and decrease particle size of FA at 90 W for 30 minutes. Chemical, physical and mineralogical compositions of FA, MFA and solid residues (SR) were determined using arrays of X-ray fluorescence (XRF), Brunauer-Emmett-Teller (BET), scanning elec- tron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) techniques and par- ticle size analysis. The removal efficiency of Al, Fe, Mn, Ni, Zn and SO4 2− from AMD was compared using FA and MFA. According to the obtained results, ultrasound-assisted MFA provided successful results for metal removal in a shorter reaction time and with smaller dosage than FA. As the pH of the solution (ash:AMD) increased, the metal and SO4 2− concentrations in SR increased mainly due to precipitation; this data was verified with XRD and XRF analysis. Preliminary treatment of AMD from Etili coal mine (NW Turkey) indicates that MFA could be an effective and low-cost adsorbent for the treat- ment of AMD.