Optimization of the Conditions for the Process of Precipitating the Hydroxide of Metals - Heavy Metals Chromium And Nickel Is Gradually In Electroplating Liquid Waste

Abstract

This study aims to determine the optimum conditions which include pH, temperature, time, and speed of stirring the process of the deposition of heavy metal chromium (Cr) and nickel (Ni) hydroxides in electroplating wastewater. So as to minimize the concentration of heavy metals chromium and nickel in electroplating wastewater before being discharged into the environment. The liquid waste sample in the beaker is stirred using a magnetic stirrer with a constant stirring speed while adding 10% ammonia solution slowly with a variation of pH: 7; 7.5; 8; 8.5; 9; 9.5; 10; 10.5; and 11. The solution is added by the pH buffer and then the volume is equaled to 200 ml, after that it is allowed to stand for 24 hours then the filtrate and the precipitate are separated. The filtrate analyzed the residual content of Cr and Ni using atomic absorption spectrophotometry (AAS). To find out the other optimum conditions, variations in temperature, time and speed of stirring of the deposition process were carried out. The results showed that the optimum pH of deposition of heavy metals Cr was achieved at pH 9 with% deposition of 79.013% while Ni at pH 9.5 with the amount of deposited Ni 99.71%. Optimum settling temperatures for Cr and Ni were reached at 100 0C with Cr% deposition at 50.304% and Ni at 97.891%. The optimum deposition time for Cr is 60 minutes with the amount of precipitation of 45.542% while the optimum deposition time of Ni for 40 minutes with% precipitation of 99.633%. The stirring speed of the Cr and Ni deposition process is 800 rpm with the amount of Cr settling at 63.493% while Ni at 98.531%.