Effect of aluminium incorporation on physicochemical properties and patent blue V photodegradation of magnesium phosphate materials

Abstract

A series of magnesium phosphate samples modified by incorporation of aluminium, denoted MgAlP-x (where x indicates the Al molar ratio%; x = 0; 10; 20; 40%), have been prepared by coprecipitation method followed by characterization. Their structures have been investigated by using powder X-ray diffraction, the surface area by physisorption of nitrogen (BET), Fourier transform infrared (FTIR) were used to characterize the functional groups of solids and MAS–NMR spectroscopy. X-ray diffractograms for synthesized materials suggest the formation of mixed solids, such as Mg3(PO4)2, AlPO4 and Al2O3. Incorporation of aluminium into magnesium orthophosphate increased the temperature of crystallization, so that MgAlP-x systems retained amorphous up to 973 K. The specific surface area increases with aluminium content. 31P MAS–NMR spectra of calcined MgP shows a single peak at δ = +0.4 ppm and two overlapped signals for calcined MgAlP-x (x = 20 and 40%). But the dry solids present more than a single peak. The varying values of chemical shifts are due to the existence of different types of 31P structural configurations and oxygen environment. 27Al MAS-NMR spectra of sample exhibit two peaks, which were characteristic of the octahedral and tetrahedral environments of Al3+ ions. It was observed that the incorporation of Al in MgP material decreases the patent blue V (PB) photodegradation. The highest dye degradation was obtained over the MgP catalyst (without Al). No correlation between the adsorption before UV irradiation and the rate of photodegradation.