A method for producing calcium fluoride from waste LCD panel glass etchant

Abstract

The invention relates to a method for producing calcium fluoride from waste LCD panel glass etching solution, which comprises the following steps in turn: take a certain amount of waste LCD panel glass etching solution, add sodium fluoride solid, and fully stir to make hexafluoride in the waste liquid Complete reaction of silicic acid and sodium fluoride to generate sodium hexafluorosilicate and hydrofluoric acid, complete reaction of hexafluoroaluminate and sodium fluoride to generate sodium hexafluoroaluminate and hydrofluoric acid, and then add ammonia water to react to generate silicon dioxide , sodium fluoride and ammonium bifluoride, so that sodium hexafluoroaluminate and the remaining sodium hexafluorosilicate settle rapidly, then filter the precipitate, take the supernatant and add it to the calcium hydroxide suspension until pH = 5 to stop, and make the hydrogen Calcium oxide completely reacts with hydrofluoric acid to generate calcium fluoride, then add calcium hydroxide suspension to make sodium fluoride and ammonium bifluoride react with calcium hydroxide to generate calcium fluoride, then add polyacrylamide solution, precipitate, filter and washing, and finally drying to obtain calcium fluoride solid. The purity of calcium fluoride can reach more than 95%.

Description

technical field [0001] The invention relates to a method for processing glass etching liquid, in particular to a method for producing calcium fluoride from waste LCD panel glass etching liquid. Background technique [0002] In the general glass thinning process, hydrofluoric acid is used to etch and thin the glass. The waste solids and waste liquids generated during the glass etching process are basically recycled by qualified third-party institutions, and then processed after recycling. The sludge is disposed of by landfill or high-temperature calcination, and the supernatant is returned to the industrial sewage treatment system for reprocessing. [0003] At present, the common treatment method of fluorine-containing wastewater is to dissolve the calcium-containing agent into a liquid first, and then add it to the wastewater under the action of mechanical stirring, so that the fluoride ions in the wastewater react with calcium ions to form water-insoluble calcium fluoride s...

AI Technical Summary

Problems solved by technology

However, the system still has the following deficiencies: 1. The calcium fluoride produced by waste acid treatment has low purity, and is usually only treated as general waste landfill, which cannot be reused as a resource, resulting in a huge waste of fluorine resources; 2. Direct dry material dosing The peritectic reaction caused by the fast precipitation reaction and the slow dissolution process will cause excessive input of dry materials and waste, which will greatly increase the amount of raw materials and production costs.