PRECIPITATION OF SOLID PHASES IN REACTION ZONE BETWEEN ACID INDUSTRIAL WASTE AND NEUTRALISATION SOLUTIONS

František Eichler ¹, Jirí Ditz ²

¹ Jáchymovská 282, 460 10 Liberec 10, Czech Republic
² VÚANCH, Výzkumný ústav anorganické chemie a.s., Revoluení 84, 400 01 Ústí nad Labem, Czech Republic

Keywords: acid industrial waste, neutralisation process, pH indicators, precipitated and coprecipitated solid phases, system solid phase-amourphous phase-liquid phase

Interaction between acid industrial waste and neutralisation solutions has been studied under light microscope as a result of chemical staining techniques. Acid industrial waste may be defined as the thermodynamic system (NH₄)₂SO₄-Al₂(SO₄)₃-H₂SO₄-H₂O and neutralusation solution by system Na₂CO₃-H₂O. Chemical process from pH< 1 in acid industrial waste to pH > 7 in neutralisation solution, and some local changes in chemical composition of liquid phase are stained by Bromocresol Blue as pH indicator. A variety of precipitated and coprecipitated solid phases dependent on pH of liquid phase as Al(OH)₃, Al₂(SO₄)₃.17H₂O and (Na, NH₄)Al(SO₄)₂.12H₂O were identified by XRD, FTIR, light microscopy, electron microscopy and electron microanalysis. Crystal structure parameters of selected well-crystallised phases are refined by Rietveld method. It is shown that the relative disttribution of Al between various complexes dictates dissolution and precipitation of components from reaction zone in system solid phase-amorphous phase-liquid phase. Time-dependent chemical processes are documented as colour changes of Bromocresol Blue on colour photos.