Highly Efficient Removal of Cd (II) Ions from Aqueous Solutions Using Hydrated Lime as a Precipitating Agent

Rapid industrialization has led to the creation of large amounts of wastewater containing various pollutants, among which heavy metals stand out. Heavy metals such as Cd (II) ions cause serious chronic diseases and even death if they are present in high concentrations. Therefore, this manuscript investigates the possibility of Cd (II) ion removal by precipitation method using Ca(OH)2. In order to optimize the precipitation process, the following were investigated: initial pH, initial concentration of Cd (II) ions, dose of added Ca(OH)2, stirring speed and contact time, as well as the influence of competing ions on the removal efficiency of Cd (II) ions. The optimization of the precipitation process was performed by varying one operational parameter at a time, while keeping all other parameters constant. Results of Cd(II) ion removal efficiency and optimal conditions are: pH 5 (99.961%), stirring speed of 0 rpm (99.985%), contact time metal-precipitant 5 minutes (99.965%), added dose of Ca(OH)2 60 mg (99.965%). Complete removal of Cd (II) ions was achieved at a Cd(II) ion concentration of 10 ppm, and high removal efficiency was achieved at concentrations of 50-300 ppm (98.231-99.994%). The removal efficiency of over 99% of Cd (II) ions was achieved during individual tests of ion competitiveness. Therefore, it can be concluded that under the tested conditions, Ca(OH)2 is an effective agent for removing Cd (II) with an efficiency above 99%.