Granulated blast-furnace slag as sorbeht of organic dyes

Abstract

The properties of granulated blast-furnace slag from “ArcelorMittal Kryvyi Rih”, which stipulate its sorption activity, have been determined. The following minerals were identified in the slag fractions: akermanite Ca2MgSi2O7, helenite Ca2Al(Al,Si)2O7, rankinite Ca3Si2O7, pseudo-wollastonite CaSiO3, merwinite Ca3MgSi2O8, microcline КAlSi3O8, calcite CaCO3, aldhamite CaS with > 50% of calcium and magnesium aluminosilicates. Some phases are in an amorphous sorption-active state. The expediency of activation with water for 1 day is shown, due to which hydroxyl and silanol groups are formed and dissociated on the surface with the formation of a negative charge on the surface of slag particles, which is typical for Ca and Mg aluminosilicates. The shape of the adsorption isotherm indicates the formation of polymolecular layers of the methylene blue (MB) organic dye, which increases the efficiency of the slag sorbent. The adsorption value of MB is not less than 2 mg/g. There is obviously no desorption of MB from the slag, which ensures the safety of both the disposal of the waste sorbent and its utilization as a filler for construction materials. The radiation safety of the slag has been proven. The specific effective activity of slag fractions does not exceed 370 Bq/kg, which allows using them as technical materials without restrictions. A technological scheme of adsorption purification of wastewaters from organic synthesis enterprises and textile industry containing organic dyes, is suggested using a slag sorbent. The stages of the technological process are the following: receiving the slag from the dump, analysis of the mineral composition of the slag, water activation of the slag, static sorption of dyes in the sump, further utilization of the slag and the inflow of purified water into the primary production. The technology provides for the removal of organic dyes from wastewater and its repeated usage, which ensures the closed cycle of water reuse, no need for chemical reagents for the activation of the slag sorbent, improvement of the environmental situation in the locations of the slag dumps due to the use of slags as sorbents.