Method of removing heavy metal from wastewater

A method of removing a heavy metal from a wastewater, comprising:

• adding a chelating agent to the wastewater to obtain a mixture;
• mixing CO2 with the mixture to reach an alkaline pH to generate a carbonic mixture;
• and
• precipitating the carbonic mixture to generate a mineral entrapping the heavy metal,
• wherein the chelating agent is present in the wastewater at an amount of 0.1 to 15 wt. % based on the total weight of the wastewater;
• wherein the wastewater comprises an alkali metal and an alkaline earth metal;
• wherein the heavy metal, the alkali metal, and the alkaline earth metal are in the form of water-soluble salts;
• wherein the chelating agent is at least one selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), gluconic acid, citric acid, and phytic acid;
• wherein the CO2 is in the form of a gas consisting essentially of CO2 at a pressure of 10 to 100 psi, and the mixing includes sparging the CO2 into the mixture with a flow rate sufficient to distribute the CO2 evenly into the mixture;
• wherein the carbonic mixture has a pH of 8 to 12;
• and
• wherein the heavy metal is present in the mineral in an amount of 0.001 to 1 wt. % based on the total weight of the mineral after precipitating.