US-12617681-B2 - Method of removing hydrogen peroxide from sulfuric acid

Abstract

A method of removing hydrogen peroxide from sulfuric acid includes the following steps: First step of pouring the sulfuric acid having 0.1 wt % to 10 wt % of hydrogen peroxide into a vessel. Second step of adding a catalyst containing copper and a copper compound to the vessel to undergo a reaction with the sulfuric acid to remove the hydrogen peroxide from the sulfuric acid, to generate heat, and to generate metal ions in the sulfuric acid. Third step of activating a cooling device to cool the vessel to a predetermined temperature range. Fourth step of adding hydrogen sulfide to the vessel to undergo a reaction with the metal ions to generate metallic sulfide and metal free sulfuric acid. Fifth step of purifying the metallic sulfide and the metal free sulfuric acid to obtain purified metallic sulfide and purified sulfuric acid as products.

Inventors

• Cheng Ming Huang

Assignees

• Cheng Ming Huang

Dates

Publication Date

20260505

Application Date

20230629

Claims (1)

1. 1 . A method of removing hydrogen peroxide from sulfuric acid, comprising the steps of: (i) pouring the sulfuric acid (H 2 SO 4 ) having 0.1 wt % to 10 wt % of hydrogen peroxide (H 2 O 2 ) into a vessel; (ii) adding a catalyst containing cupric oxide to the vessel to undergo a reaction with the sulfuric acid (H 2 SO 4 ) to remove the hydrogen peroxide (H 2 O 2 ) from the sulfuric acid (H 2 SO 4 ), to generate heat, and to generate metal ions in the sulfuric acid (H 2 SO 4 ); (iii) activating a cooling device to cool the vessel to a predetermined temperature range; (iv) adding hydrogen sulfide (H 2 S) to the vessel to undergo a reaction with the metal ions to generate metallic sulfide and metal free sulfuric acid (H 2 SO 4 ); (v) purifying the metal free sulfuric acid (H 2 SO 4 ) to obtain purified metallic sulfide and purified sulfuric acid (H 2 SO 4 ) as products; and (vi) adding activated carbon to the products for absorbing smell.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part (CIP) of U.S. patent application Ser. No. 17/028,989, filed Sep. 22, 2020, now abandoned, which is incorporated herein by reference in its entirety. BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to methods of removing hydrogen peroxide from sulfuric acid and more particularly to a method of removing hydrogen peroxide from waste sulfuric acid so that products (e.g., copper (II) sulfide (CuS) of high purity and highly purified, diluted sulfuric acid (H2SO4)) can be reused. 2. Description of Related Art Conventionally, sulfuric acid of high purity is used to clean the surface of an etched silicon wafer in a semiconductor manufacturing process. Hydrogen peroxide (H2O2) is added to the sulfuric acid (H2SO4) to form a strong oxidizing agent which is adapted to oxidize organic substances of the wafer into CO2 and H2O. At the end of the process, waste sulfuric acid (H2SO4) is generated. The waste sulfuric acid comprises 40 wt %-80 wt % of sulfuric acid (H2SO4), 4 wt %-8 wt % of hydrogen peroxide (H2O2), and water being the remaining substance in terms of concentration. However, there are contaminants in the waste sulfuric acid. The hydrogen peroxide (H2O2) in the contaminants is a strong oxidizing agent and can limit reusability of the sulfuric acid (H2SO4). Thus, the waste sulfuric acid cannot be used again for clean wafers in the semiconductor manufacturing process. Conventionally, the hydrogen peroxide (H2O2) is removed from the waste sulfuric acid with other products being generated for reuse in a semiconductor manufacturing company. Conventionally, there are many methods of removing hydrogen peroxide from waste sulfuric acid. One of the most widely used methods comprises the step of adding hydrochloric acid (HCl) in the waste sulfuric acid to undergo a reaction with the hydrogen peroxide (H2O2). It is noted that hydrochloric acid (HCl) is both a reactant and a catalyst. The expression is shown below. H2O2+2HCl→Cl2(g)+2H2O The other most widely used method comprises the step of adding activated carbon or enzyme to the waste sulfuric acid to undergo a reaction with the hydrogen peroxide (H2O2) for dissolving the hydrogen peroxide (H2O2). The conventional methods of removing hydrogen peroxide from waste sulfuric acid have the following drawbacks: While certain amount of hydrogen peroxide (H2O2) can be removed from the waste sulfuric acid by adding hydrochloric acid (HCl) to the waste sulfuric acid, there is diluted sulfuric acid (H2SO4) having chlorine ions (Cl−) in the final product. The chlorine ions (Cl−) can corrode the apparatus used in the method and in turn lower the quality of the products. While enzyme added to the waste sulfuric acid can remove hydrogen peroxide from the waste sulfuric acid, the amount of the hydrogen peroxide is relatively low. Further, the chemical reaction takes a relatively long time, thereby greatly increasing the processing cost. Thus, the need for improvement still exists. SUMMARY OF THE INVENTION It is therefore one object of the invention to provide a method of removing hydrogen peroxide from sulfuric acid comprising the steps of pouring the sulfuric acid (H2SO4) having 0.1 wt % to 10 wt % of hydrogen peroxide (H2O2) into a vessel; adding a catalyst containing copper and a copper compound to the vessel to undergo a reaction with the sulfuric acid (H2SO4) to remove the hydrogen peroxide (H2O2) from the sulfuric acid (H2SO4), to generate heat, and to generate metal ions in the sulfuric acid (H2SO4); activating a cooling device to cool the vessel to a predetermined temperature range; adding hydrogen sulfide (H2S) to the vessel to undergo a reaction with the metal ions to generate metallic sulfide and metal free sulfuric acid (H2SO4); and purifying the metal free sulfuric acid (H2SO4) to obtain purified metallic sulfide and purified sulfuric acid (H2SO4) as products. The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart of a method of removing hydrogen peroxide from sulfuric acid according to the invention; and FIG. 2 is a table of test reports regarding the invention. DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, a method 1 of removing hydrogen peroxide from sulfuric acid in accordance with the invention is illustrated and comprises the steps of S1 pouring the sulfuric acid (H2SO4) having 0.1 wt % to 10 wt % of hydrogen peroxide (H2O2) into a vessel; S2 adding a catalyst containing copper and a copper compound (e.g., cupric oxide (CuO)) to the vessel to undergo a reaction with the sulfuric acid (H2SO4) to remove the hydrogen peroxide (H2O2) from the sulfuric acid (H2SO4), to generate heat, and to generate metal (e.g., copper (Cu)) ions in the sulfuric acid (H2SO4); S3 activating a cooling