Patent ID: 9458038
Filing Date: 2016-10-04
CPC Classification: C01B,C01F,C01G,C01P,C02F,Y02W

Claim Text:
1. A wastewater treatment process in which a first neutralizing agent is added into sulfuric acid-acidic wastewater containing aluminum, magnesium, and manganese to separate an aluminum hydroxide precipitate and obtain a solution after dealumination, then a second neutralizing agent and an oxidizing agent are added to the solution after dealumination to separate a manganese precipitate and obtain a solution after demanganization, and then a third neutralizing agent is added to the solution after demanganization to obtain a wastewater precipitate and effluent wastewater, comprising, using for part or all of first to third neutralizing agents to be added a magnesium oxide produced through steps (1) to (4): (1) a calcium separation step of concentrating effluent wastewater obtained by separating aluminum and manganese from sulfuric acid-acidic wastewater, and precipitating and separating calcium contained in the effluent wastewater as a calcium sulfate; (2) a magnesium crystallization step of further concentrating a solution obtained through the calcium separation step, and precipitating and separating magnesium contained in the solution as a magnesium sulfate; (3) a roasting step of roasting the magnesium sulfate separated in the magnesium crystallization step together with a reducing agent, and obtaining a magnesium oxide and sulfurous acid gas; and (4) a washing step of washing the magnesium oxide obtained in the roasting step.