An attapulgite composite with high degradation performance for Congo red without using oxidants and photoexcitation

Abstract

Dye wastewater poses a serious threat to water resources and the removal of dye molecules from dye wastewater has attracted much attention. In this work, attapulgite (ATP) mineral nanomaterials were firstly grafted with magnetic Fe3O4nanoparticles and then modified with polyethyleneimine (PEI) to prepare functionalized magnetic attapulgite composites (ATP-Fe3O4-PEI), which was used for the treatment of Congo red (CR) dye wastewater. The structure and surface properties of the composites were analyzed and characterized through FT-IR, XRD, SEM, TEM, BET analysis, zeta potential measurement, and VSM analysis. The removal performance of ATP-Fe3O4-PEI for CR was studied, and the removal mechanism was explored and revealed as well. It was believed that the CR removal by ATP-Fe3O4-PEI was mainly by a catalytic degradation process. Without photoexcitation and addition of oxidants in the solution, the system itself could produce H2O2 and hydroxyl radicals (·OH) to catalytically degrade the CR molecules. In addition, the removal of CR was further enhanced by adsorption of the composite material through electrostatic attraction, hydrogen bonds, and π-π interaction. Under the two removal behaviors, the removal rate of ATP-Fe3O4-PEI for CR was more than 95 % corresponding to a removal capacity of 943.77 mg·g−1 at pH = 3 and 25 °C. Moreover, the prepared ATP-Fe3O4-PEI materials have good recyclability with a removal rate and removal capacity above 82% and 799 mg·g−1 after 4 cycles. Within our best knowledge, this is the first report on the degradation of dye compounds by advanced oxidation without using oxidants and photoexcitation.