Abstract
The paper presents research results concerning charge composition development to produce environmentally safe acid-resistant ceramics on the basis of low-plastic clay of the Vladimir region possessing self-glazing effect. 5 wt. % boric acid, 5 wt. % lanthanum oxide and up to 5 wt. % electroplating sludge have been introduced into the charge composition as functional additives. Boric acid serves as a flux and a source acid-resistant and heat-resistant vitreous phase based on borosilicates, but compositions contained in the electroplating sludge are decomposed in the process of ceramics firing causing the formation of calcium oxide and heavy metal oxides, which additionally increase material acid-resistance and heat-resistance like lanthanum oxide. To receive the developed material, semidry pressing technology has been applied under the charge forming moisture of 8 wt. %, specific pressure of 15 МPа and one-stage firing at max temperature of 1050 °C. The research presents the testing results of ceramics principal operating properties and environmental safety. The developed material can be used in clinker and acid-resistant bricks and tiles production for masonry and tiling in aggressive environment like buildings foundations and bases, premises with high moisture, as well as in sewerage systems, chimneys and ventilation ducts.
Highlights
Heavy metals are known to refer to the metals of 50 AWU
The choice of boric acid amount was proved by the previous experiments which demonstrated that big amount of acid does not considerably change the produced ceramics characteristics and the excess of the vitreous phase causes deformation, but small amount leads to ceramics lower pressure strength and higher water absorption [4]
It depends on the heavy metals hydroxides and calcium carbonate presence in the sludge which decompose in the process of ceramics firing releasing water vapor and carbon dioxide enhancing material porosity and reducing its strength
Summary
Heavy metals are known to refer to the metals of 50 AWU. They differ in their high density and good electric conductivity. They include refractory and low-melting, hard and plastic metals. Heavy metals and they compositions are widely applied in metallurgy, machine-building, chemical and electrochemical industries, in textile, glass, ceramics, polymer production and pharmaceutics. Heavy metals and their compounds are applied in construction and in electrotechnical units production. They are used as functional additives like fillers, stabilizers etc
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