Statistical optimization of amorphous iron phosphate: inorganic sol–gel synthesis-sodium potential insertion

Abstract

Iron phosphate, Fe2 (HPO4)3*4H2O, is synthesized at ambient temperature, using the inorganic sol–gel method coupled to the microwave route. The experimental conditions for the gelling of Fe (III)-H3PO4 system are previously defined. Potentiometric Time Titration (PTT) and Potentiometric Mass Titration (PMT) investigate the acid–base surface chemistry of obtained phosphate. Variations of surface charge with the contact time, Q a function of T, are examined for time contact varying in the range 0–72 h. The mass suspensions used for this purpose are 0.75, 1.25 and 2.5 g L−1. The point of zero charge (PZC) and isoelectric point (IEP) are defined using the derivative method examining the variations $$\frac{{{\text{dpH}}}}{{{\text{d}}t}} = f\left( {{\text{pH}}} \right)$$ dpH d t = f pH , at lower contact time. A shift is observed for PZC and IEP towards low values that are found to be 2.2 ± 0.2 and 1.8 ± 0.1, respectively. In acidic conditions, the surface charge behavior of synthesized phosphate is dominated by $$\overline{{ > {\text{POH}}}}$$ > POH ¯ group which pKa = 2.45 ± 0.15. Q against T titration method is performed for synthesized Fe2 (HPO4)3*4H2O in NaCl electrolytes. The maximal surface charge (Q) is achieved at the low solid suspension. Hence, for m = 0.75 g L−1, Q value of 50 coulombs is carried at μ = 0.1 and pH around 12, while charge value around 22 coulombs is reached in the pH range: 3–10. The effect of activation time, Q and pH on sodium insertion in iron phosphate, were fully evaluated. To determine the optimal conditions of the studied process, mathematical models are used develop response surfaces in order to characterize the most significant sodium interactions according to the variation of the pH, Q, the contact time and the contents of the synthesized material.

Amorphous Iron Phosphate: Inorganic Sol-Gel Synthesis-Sodium and Potassium Insertion

“…As reported previously, an increase in iron phosphate acidity is also observed with aging time, which leads to the rising of the characteristic O-P-O bending peak at 900 cm -1 (Ellouzi et al., 2016;Maarouf et al., 2021). Two lower frequency bands occurring at 640 and 540 cm -1 are associated with bending modes of the structural OH groups and P-O bonds, respectively.…”

“…The composition and the purity of this synthesis phosphate are established using dispersive energy X-ray spectroscopy (EDX), the spectrum is presented in Figure 5. As shown, no impurities that can be attributable to contamination of chemical precursors are detected (Maarouf et al, 2021).…”

“…According to the previous study (Jarlbring et al, 2005;Jarlbring et al, 2006;Ellouzi et al, 2016;Maarouf et al, 2021) > SOH+ H + ↔ > 𝑆(𝑂𝐻 2 ) + , 𝐾 + (1) > 𝑆𝑂𝐻 ↔ > 𝑆𝑂 − + H + , 𝐾 −…”

“…Iron (III) phosphate was synthesized by a modified inorganic sol-gel method (El Yahyaoui et al., 2002;Maarouf et al., 2021). In this method, phosphoric acid (0.1 M) and iron (III) nitrate (0.1M) were used as the starting materials.…”

Surface Complexes of Cr(VI) by Eucalyptus Barks

“…Morphological surface features were examined by applying Jeol JSM-IT100 In TouchScopeTM Scanning Electron Microscope (SEM) connected to a microanalyzer EDS [39]. Analysis of the dosage of chromium(VI) is carried out in the aqueous phases before and after adsorption by a (EPA 7196A) UV-Visible spectrophotometer.…”