WITHDRAWN: Effects of pH on Ochrobactrum immobilises heavy metals during fly ash–sludge​ co-pyrolysis

Abstract

In order to determine the optimal pH at which Ochrobactrum immobilises heavy metals during fly ash-sludge co-pyrolysis, we investigated the effects of pH on Ochrobactrum to adsorb or desorb heavy metals. The metallic forms of copper (Cu), zinc (Zn), and manganese (Mn) under different pH conditions during co-pyrolysis were analysed using the sequential extraction procedure (BCR). The stabilising mechanisms of Cu, Zn, and Mn caused by Ochrobactrum under different pH conditions during co-pyrolysis were characterised with Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Results indicated the following: (1) The heavy metals immobilised by Ochrobactrum were significantly affected by pH during fly ash-sludge co-pyrolysis. (2) The stable forms of Cu, Zn, and Mn increased most noticeably under neutral and weak alkaline conditions. (3) The neutral and weak alkaline conditions favoured the formation of crystallised materials as well as the preservation of chemical bonds. The results suggested that the effects of Ochrobactrum on the immobilisation of Cu, Zn, and Mn under neutral and weak alkaline conditions were optimal. The results of the study can provide a reference and basis for the harmless disposal of municipal sludge and fly ash and the efficient utilisation of Ochrobactrum . • pH had an effect on Ochrobactrum during fly ash-sludge co-pyrolysis. • pH 7 and pH 9 could improve the stabilisation of heavy metals by Ochrobactrum . • pH 7 and pH 9 could promote the preservation of the chemical bonds by Ochrobactrum . • pH 7 and pH 9 could promote the formation of crystallised materials by Ochrobactrum .