One-step removal of organic matter and heavy metals from Tunisian oil field (TOF) produced water using soluble sodium silicate with a unit molar ratio SiO 2 /Na 2 O

Oil field wastewater (produced water) management is a crucial environmental issue due to its hydrocarbons content, heavy metal, and high salinity. In this study, soluble sodium silicate was used, under controlled conditions in laboratory, for treating generated water from a petroleum field situated in Southern Tunisia. The efficiency of soluble sodium silicate (Na 2 SiO 3 ) in the removal of organic matter and heavy metal from produced wastewater was investigated, the optimization of the proposed process (Na 2 SiO 3 dose , agitation speed, and required treatment time). Soluble sodium silicate (SiO 2 /Na 2 O = 1) at a dose of 1%, low agitation (50 rpm), and a treatment duration of only 5 min achieved a high removal efficiency for simultaneous removal of chemical oxygen demand(COD) and major heavy metals. The removal yield of contaminant could reach up to 97%. Instantaneous chemical precipitation and adsorption onto calcium silicate are the main processes that yielded a high removal rate of organic matter and heavy metals. Silica and calcium silicate with absorbed contaminants were found to be the two stabilized by-products that could safely be dumped at landfill sites. Sludge by-product was carefully investigated with FTIR analysis, XRD and SEM-EDAX. The silicate-derived component along with co-precipitated calcium carbonate and sodium chloride are the main recognized salts.