Chemical precipitation approach to the removal of heavy metals from wastewater for discharge into sanitary sewerage

Abstract

NaOH, Ca(OH)₂ and Na₂CO₃ were used as the precipitants in this study. The reaction time was set at 45 min, temperature at 50º C, pH at 9 for the hydroxides and 10 for the carbonate. Heavy metal ions precipitated includes; Pb²⁺, Cu²⁺, Mn²⁺, Zn²⁺ and Fe³⁺. NaOH exhibited highest precipitation for Cu²⁺ (99.2 %) and least for Zn²⁺ (75.2 %), Ca(OH)₂ exhibited highest precipitation for Cu²⁺ (100 %) and least for Pb²⁺ (71.9 %), while Na₂CO₃ exhibited highest precipitation for Fe³⁺ (97.6 %) and least for Pb²⁺ (75 %). The precipitation of all the heavy metals ions were also compared for the precipitants. All precipitant are capable of removing at least 70% of the heavy metal ions studied form their aqueous solution while a narrow selection might take the value as high as 100%, hence showing adequate potentials of the precipitants in the removal of aqueous heavy metal ions at the set conditions form wastewater prior to discharge into sewerage.