Study On The Gelation Of Electroplating Wastewater And Its Application In Glass

Electroplating wastewater is harmful to the environment and human body.At present,it is mainly treated by adsorption and chemical precipitation in electroplating plants.But the wastewater after treatment by these methods still needs to be further treated in water treatment plant.In addition,secondary pollutants such as sludge will also be produced after the treatment.In this paper,water glass and sodium meta-aluminate were used to gelate the electroplating wastewater.The formed gel powders were then used in the preparation of glass materials.There was no secondary pollution in the whole process,and waste was turned into resoures.This study provides a new idea for the treatment of electroplating wastewater.In the experiments,an acidic copper electroplating wastewater was gelated with water glass solution by sol-gel method.When the volume ratio of copper electroplating wastewater to water glass was 3:2,the minimum gelation time was 6 h,and water bound in the gel was43.29%.However,the sulphur content in the produced gel powder was high?7.52%?,not suitable for glass preparation.The use of barium nitrate could remove the sulfur from the copper electroplating wastewater.The gelation time of this pre-treated copper electroplating wastewater with water glass solution was shortened to 4 h.After adding calcium oxide,the gel time was further shortened to 2 h.The wet gel was dried,and the distilled water could be directly discharged.The xerogel powder obtained after the wastewater gelation treatment was heated at 750 ^oC for 30 min to obtain a foamed glass with density of 0.23 g/cm³,porosity of82.73%,and thermal conductivity of 0.07?W/?m·K??.Solutions of water glass and sodium meta-aluminate,and calcium oxide were used to gelate the acid copper electroplating wastewater after desulfurization.When the addition amount of sodium meta-aluminate was 0.8,1.2 and 1.6 ml,the gelation time was 80,60,30min.The pH,TOC,TN and the contents of ions in the distilled water recovered when the wet gel was dried meet the requirements of the standards regulating the discharge of industial water.The gel powders produced with the different addition of sodium meta-aluminate were first used to melt glass.After the melts were queched in water,glass frits were obtained.The prepared glass was tested by PCT,and its ion leaching was very low,suggesting a good chemical stability.The crystal growth index of the glasses was less than 3,indicative of surface crystallization.Glass-ceramics were then prepared via sintering the glass powders.The glass-ceramics obtained at 750°C for 60 min had the best performance,with density of2.57 g/cm³,hardness of 569.23×10⁷ Pa,and the main crystal phase of sodalite.When the volume ratio of electroplating chrome wastewater to water glass solution was2:1,the gelation time was 5min at the shortest,forming a chrome-containing gel.The evaporating water generated during the drying of the produced wet gel met the wastewater emission standards.Colored glasses were prepared by the addition of different amounts of chrome-containing gel to a basic silicate glass batch.The visible light spectra of the prepared glass was mesured,characterizing their green color.As the amount of colorant was increased,the light transmittance of the glass decreased and the color increased.The chrome-containing gel was used to introduce Cr₂O₃ as a nucleating agent for glass.When the introduced Cr₂O₃was less than 2%,surface crystallization was evidenced for the prepared silica glass.When the amount was 2%,surface crystallization was shown for the glass,and the crystal phase was pyroxene and anorthite.