Chelation of metal ions with citric acid in the ammoniation process of wet‐process phosphoric acid

Abstract

A new process is proposed in which citric acid is added during the ammoniation process of wet-process phosphoric acid (WPA) to chelate metal ions to produce fertilizer ammonium dihydrogen phosphate (MAP) containing medium trace elements. The parameters of the chelation reaction were studied systematically and the results show that the optimal reaction condition is pH 3.0, reaction time 60 minutes, temperature 50.0 C, and citric acid content 1.48%. The XRD patterns show that the waterinsoluble compounds are complex mixtures, and the composition of the waterinsoluble compounds are changed through the addition of citric acid. FTIR and XPS analyes further demonstrate that water-insoluble compounds are complex mixtures. The XRD patterns of the MAP products indicate that the structure and morphology of the MAP were changed by the addition of citric acid. In addition, the contents of major elements, medium elements, and trace elements in the MAP product are 68.72%, 0.24%, and 0.50%, respectively, which is consistent with the relevant China national standard. K E Y W O R D Sammonium dihydrogen phosphate, chelation, citric acid, wet-process phosphoric acid

Valorization of Byproducts from Hydrothermal Liquefaction of Sewage Sludge and Manure: the Development of a Struvite-Producing Unit for Nutrient Recovery

“…CA was added in the amount of 2 mol of CA in a concentration of 1 mol·L –1 per sum of moles of aluminum and iron ions in the leachate . CA is known as a promising biodegradable complexing agent, and it can form stable soluble complexes with diverse metal cations, such as Al, Fe, Ca, and Mg. − As a result, the metal cations become inaccessible for precipitation and binding with phosphate ions. Figure demonstrates that the use of CA resulted in a distinct increase in struvite content in the precipitate (more than 90 wt %).…”

“…This inhibition may be attributed to the selective adsorption and binding of free CA to the faces of the struvite with a high density of magnesium and ammonium cations. As a result, the active crystal growth sites are blocked. ,, Furthermore, the CA can react with Mg 2+ and NH 4 + to form [C 3 H 5 O­(COO) 3 ] 2 Mg 3 and C 3 H 5 O­(COO) 3 (NH 4 ) 3 , which may reduce the supersaturation level for struvite. , The changes in solution pH and concentration of Al, Fe, and Ca ions by their partial precipitation may influence the stability of the metal complexes and move the equilibrium in the complex formation reaction toward de-coupling. As a result, free CA can be released and affect struvite formation, as described above.…”

“…40,41,69 Furthermore, the CA can react with Mg 2+ and NH 4 + to form [C 3 H 5 O(COO) 3 ] 2 Mg 3 and C 3 H 5 O(COO) 3 (NH 4 ) 3 , which may reduce the supersaturation level for struvite. 40,41 The changes in solution pH and concentration of Al, Fe, and Ca ions by their partial precipitation may influence the stability of the metal complexes 67 and move the equilibrium in the complex formation reaction toward de-coupling. As a result, free CA can be released and affect struvite formation, as described above.…”

Crop root Exudate Composition‐Dependent Disassembly of Lignin‐Fe‐Hydroxyapatite Supramolecular Structures: A Better Rhizosphere Sensing Platform for Smart Fertilizer Development

“…suggesting that lignin-Fe coordination is more disrupted in the presence of organic acids rather than only H + ion. Given that organic acids can chelate metallic ions, [39] citric acid would aid to extract ferric ions from the supramolecular assembly and act as a competitor to lignin components. Another clue supporting the role of organic acids was obtained by performing a SEC.…”

Influence of pollutant concentration on the separation efficiency of chelating membranes for removing simultaneously metal ions and proteins from simulated industrial wastewater

“…They primarily come from urban sewage 18 and industrial effluent 19 of the food industry, pharmaceutical industry, paper industry, pesticide industry, paint industry, etc. At present, chemical precipitation, 20,21 chemical reduction, 22,23 chelation, 24 adsorption 25 and membrane separation 26 usually are used for the removal of metal ions from wastewater. Likewise, there are many ways to deal with organic pollutants, including physical adsorption, 27 chemical reaction, 28 flocculation, 29 sedimentation, 30 membrane separation, 31 etc.…”