New Organic Compounds Detection and Potential Removal in Crude Phosphoric Acid using Waste Sludge

Abstract Some organic compounds in phosphoric acid are a potential mediator of adverse environmental impacts on soil. This work aims to detect and reduce the content of organic compounds in crude phosphoric acid using waste sludge, from water treatment plants, as a low-cost sorbent. Gas chromatography/Mass spectrometry (GC/MS) was used to detect the organic species in crude phosphoric acid, while X-ray fluorescence (XRF), X-ray Diffraction (XRD), and Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were used to characterize waste sludges. Practically, three sludge samples were utilized and different factors including shaking time, sorbent dose, and phosphoric acid concentration were studied. The results of GC/MS revealed that crude phosphoric acid contains bis [tert-butyl(dimethyl)silyl] azelaate, dibutyl phthalate, and 2,6-di-tert-butyl-4-methylphenol as the main organic species. Moreover, the clay content and the surface charge of sludge strongly affect the removal efficiency of organic species. Kinetic analysis using Lagregran pseudo-first-order, pseudo-second-order, Morris-Weber, and Elvoich models display that the sorption process using waste sludges is a chemisorption process. Finally, the three sludge samples exhibit potential sorbents for the clarification of phosphoric acid and sequentially to produce green phosphate fertilizers.