Study of Zn(II) ion removal from galvanic sludge by geopolymers

Abstract

The galvanic sludges contain a number of toxic heavy metals, potentially mobilized as chemically active ions under environmental conditions as. This study explores the application of fly ash-based geopolymers for the removal of Zn ions from galvanizing sludge. In this study, geopolymers, synthesized via the geopolymerization method, were used to remove Zn from post-galvanized sewage sludge. Two types of geopolymers were used, derived from ash from coal combustion and biomass combustion. Structural, morphological, and surface properties were characterized using FTIR and SEM, respectively. In addition, BET and Langmuir isotherms, along with analyses such as t-Plot and BJH method for porous solids were conducted. The results indicate that the geopolymer derived from coal combustion ash is a more effective sorbent for Zn(II) ions, exhibiting a removal efficiency of 99.9%, compared to 40.7% for the geopolymer derived from biomass combustion ash. The FTIR spectra analysis reveals the presence of bonds between the -OH and/or Si-OH groups on the geopolymers' surface and the Zn(II) ions. The environmentally and economically advantageous process maximizes the recovery of a valuable component at minimal cost, yielding relatively clean monometallic waste suitable for reuse.