Abstract
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), scanning electron microscope equipped with energy-dispersive X-ray (SEM/EDAX) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were used to characterise waste sludges. Practically, three sludge samples (S1 from El-Marg, S2 from Al-Obour and S3 from El-Sheikh Zayed stations, respectively) were utilised 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 Lagergren pseudo-first-order, pseudo-second-order, Morris-Weber and Elovich models displays that the sorption process using waste sludges is a chemisorption process. The sorption capacity of the applied three sorbents was 26.3, 23.3 and 22.8 mg/g for S1, S2 and S3, respectively, which indicates that the three sludge samples exhibit potential sorbents for the clarification of phosphoric acid and sequentially to produce green phosphate fertilisers.
Highlights
Phosphorus (P) is one of the vital macronutrients required for plant growth as well as human life.Phosphorus was utilized for increasing crop products since the 1950s (Stewart and Roberts 2012)
Elvoich models display that the sorption process using waste sludges is a chemisorption process
The mean diameter of the sludge particles was determined at 170°, by dynamic light scattering (DLS)
Summary
Phosphorus (P) is one of the vital macronutrients required for plant growth as well as human life. Phosphorus was utilized for increasing crop products since the 1950s (Stewart and Roberts 2012). The. United Nations reported that the world population is expected to become about 9 billion by 2050, and the food demand will increases by 60% for the same period that sepsequently will rise the global phosphors demand (FAO 2018). Phosphorus security is considered one of the greatest global sustainability challenges in the twenty-first century (Cordell and White 2014). Phosphorus management is very important for sustainable food and agriculture, in food-deficient and phosphorusscarce countries (Cordell et al 2015). Phosphate rock is a nonrenewable natural resource that is used to describe phosphate-bearing minerals
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