One-Pot Synthesis and Hydrolysis Behavior of Highly Water-Soluble Ammonium Polyphosphate

Abstract

Ammonium polyphosphate (APP) exhibits high water solubility, mobility, and slow-release properties, which can greatly improve the utilization of phosphorus by alleviating soil phosphorus fixation. However, obtaining an efficient method of preparing APP that involves low energy consumption and production cost remains a challenge in current industrial production. Herein, by using urea phosphate (UP) as the main feedstock, we established a simple one-pot method for synthesizing highly water-soluble APP and explored the regulatory mechanism of the reaction temperature, the ratio of urea phosphate to monoammonium phosphate (MAP)/potassium dihydrogen phosphate (MKP), and the reaction time on APP performance. After analyzing the products obtained from different reaction conditions, we classified the polymerization process into the following stages: chain generation and chain growth. The chain generation reaction occurs simultaneously with the chain growth reaction, and the chain growth reaction tends to dominate with further reaction time. Furthermore, the optimum processing conditions for industrial production were obtained by comparing product performance, and the resulting APP products exhibit the following characteristics: the N and P contents were 20.6% and 58.8%, respectively, the polymerization rate (Pr) was 93.6%, the degree of polymerization was 4.22, and the solubility was 263.91 g/100 g H2O. Finally, to characterize the stability of the APP liquid fertilizer, we further investigated the hydrolysis behavior of APP and obtained the apparent activation energy (E a = 93.17 kJ/mol) of APP hydrolysis and the evolution of polymerization degree distribution of APP at different pH values. Overall, our results indicate that low temperature and alkaline conditions can greatly prolong the storage time of ammonium polyphosphate-based liquid fertilizers, which provides a basis to compound highly concentrated ammonium polyphosphate-based liquid fertilizers.

Synthesis, characterization, and swelling properties of a novel tapioca-g-Poly(Acrylic acid−2−acrylamido−2−methylpropane sulfonic acid)/ammonium polyphosphate superabsorbent polymer

“…In the spectrum of TS-g-AA-AMPS/APP (curve (c)), in addition to the absorption peaks already found in TS-g-AA-AMPS, new peaks at 853 cm −1 và 883 cm −1 appear that are assigned for the asymmetric stretching vibration of P-O [27], which indicates the existence of APP (curve (d)) in TS-g-AA-AMPS/APP. Unfortunately, the peak at about 1254-1209 cm −1 [27,29] assigned to the P=O stretching vibration of APP could not be observed due to the overlap with the characteristic absorption peaks of the −SO 3 − group in the range of 1294-1156 cm −1 [19,20,38].…”

“…In the spectrum of TS-g-AA-AMPS/APP (curve (c)), in addition to the absorption peaks already found in TS-g-AA-AMPS, new peaks at 853 cm −1 và 883 cm −1 appear that are assigned for the asymmetric stretching vibration of P-O [27], which indicates the existence of APP (curve (d)) in TS-g-AA-AMPS/APP. Unfortunately, the peak at about 1254-1209 cm −1 [27,29] assigned to the P=O stretching vibration of APP could not be observed due to the overlap with the characteristic absorption peaks of the −SO 3 − group in the range of 1294-1156 cm −1 [19,20,38]. In addition, the peak at 1250 cm −1 assigned to the P=O stretching vibration of APP could not be observed because APP (n < 20) is highly water soluble with a low degree of polymerization and has the ability to absorb and water hydrolysis, which was also observed in the work of Kai Zhang et al [25].…”

“…Water-soluble ammonium polyphosphate (APP) is an inorganic polymer (low degree of polymerization, n < 20) with outstanding water solubility, non-toxic, and biodegradability. APP is an important raw material in water-soluble, chelated, and controlled-release fertilizers [24], flame retardants [25,26], emulsifiers, and food additives, and are low cost [27,28]. According to our observation, studies on the introduction of APP into superabsorbent polymer networks are rarely reported, Wang and co-workers have synthesized new semiinterlayer polymer network (semi-IPN) superabsorbent polymers with slow-release fertilizer based on corn straw cellulose polymers (CSC-g-AA/APP, CSC-g-AA/PVA-APP) [29], and millet straw-based polymer (MSPg-AA/PVA-APP) [30], prepared by solution polymerization has very good adsorption capacity in distilled water, helping to enhance soil water holding capacity and slow release of nutrients.…”

Influence and Selection of Nitrogen and Phosphorus Compound Fertilizers on Emitter Clogging Using Brackish Water in Drip Irrigation Systems

“…In this regard, UP and APP fertilizers, which have slightly higher fertilizer prices and obvious anti-clogging effects, can be used for lowconcentration fertilization. However, from the point of view of environmental impact, UP fertilizer is more suitable for alkaline soil (Cherrat et al, 2020), and APP fertilizer, with good water solubility and chelating effect, is also more suitable for alkaline soil compared with acidic soil (Wang et al, 2022a). As a kind of highly efficient and environmentally friendly composite fertilizer, MAP is widely used in agriculture (Pizzeghello et al, 2019).…”