Magnesium hydroxide (MH) nanoparticles are environmentally friendly inorganic flame-retardants with excellent smoke suppression and broad application prospects in polymers. To address the pollution caused by traditional halogen/phosphorus flame-retardants and the agglomeration of MH during synthesis, this study employs N-methylimidazolium acrylate ionic liquid (ILA) as a crystal growth regulator, combined with an optimized room-temperature and atmospheric-pressure homogeneous precipitation method to achieve the controlled synthesis of MH. Crystallization kinetics studies via conductivity measurements reveal that ILA, through the synergistic effect of "coordination inhibition + steric hindrance", extends the crystallization induction period of MH, retards nucleation and growth rates, and reduces activation energy. Dynamic light scattering (DLS) tests show that the ILA-regulated MH has an average particle size of 154.5 nm and a zeta potential of -17.24 mV, indicating improved dispersibility. Structural characterization results demonstrate: X-ray photoelectron spectroscopy (XPS) detects 14.59% nitrogen, confirming the chemisorption between ILA and MH; scanning electron microscopy (SEM) observes a cluster-like lamellar morphology; and X-ray diffraction (XRD) indicates preferential (1 1 0) facet growth. Thermogravimetric analysis (TGA) shows that MH-ILA has a maximum decomposition temperature of 377.29 degrees C and a char residue of 56.18% at 800 degrees C. Density-functional theory (DFT) calculations suggest that ILA forms an interface with MH via Mg-O bonds, and the hydrogen bonding and pi-pi conjugation of the imidazole ring further reinforce this spontaneous chemisorption process. This work provides a sustainable strategy for the green synthesis of high-performance nano flame-retardants.

Magnesium hydroxide (MH) is a promising halogen-free flame retardant, but its practical use is often limited by aggregation arising from high surface polarity and insufficient colloidal stability. Here, two anion-tailored [BMIM]+-based ionic liquids, 1-butyl-3-methylimidazolium acrylate (ILA) and 1-butyl-3-methylimidazolium glycinate (ILB), were employed in an ionic-liquid-assisted controlled precipitation route to regulate MH crystal growth and interfacial stabilization. Under optimized conditions, MH-ILA and MH-ILB exhibited reduced average particle sizes of 93.96 and 81.68 nm and increased absolute zeta potentials of -23.37 and -31.85 mV, respectively, indicating markedly improved dispersion stability. Structural characterization further showed that ionic-liquid addition modified MH morphology, crystallographic growth, surface chemistry, and thermal behavior. DFT calculations revealed an anion-directed facet-selective growth mechanism on the MH (001) surface: both ionic liquids preferentially adsorb on this surface, whereas ILB shows stronger multi-site interactions and a more negative adsorption energy than ILA (-3.827 vs -2.738 eV), leading to more effective suppression of growth along [001]. These results establish an anion-tailoring strategy for facet-selective growth regulation and colloidal stabilization of nano-MH, and provide a mechanistic basis for designing advanced flame-retardant inorganic nanofillers.

Background: In response to the growing demand for environmentally friendly and efficient flame retardants, nano-magnesium hydroxide (nano-MH) has emerged as a promising candidate due to its high thermal stability and smoke suppression properties. However, its practical application is limited by agglomeration and high loading requirements. Methods: This study presents a controlled synthesis strategy using the ionic liquid 1-butyl-3-methylimidazolium glycinate (ILA) as a multifunctional regulator. Under optimized conditions (Na/Mg molar ratio of 2.5, 10 g/mol ILA addition, 0.4 mol/L MgSO4, reaction temperature of 50 degrees C, reaction time of 60 min), ILA enables the formation of well-dispersed hexagonal nano-MH platelets (1-5 mu m) with enhanced thermal stability and a surface nitrogen content of 9.77%. Mechanistic studies via DFT reveal a "dual-anchoring" effect. The imidazolium cation electrostatically interacts with surface OH- groups, while the glycinate anion coordinates with Mgt*, preferentially inhibiting (001) plane growth. The optimized magnesium hydroxide (MH) was combined with polyvinyl alcohol (PVA) to prepare nano-magnesium hydroxide/PVA composite materials. A comprehensive and detailed analysis was conducted from the perspectives of thermal stability, flame-retardant performance, and material morphology using thermogravimetric analysis, limiting oxygen index, horizontal burning test, micro-scale combustion calorimetry, and scanning electron microscopy. The study elucidates the influence mechanism of ILA-regulated nano-magnesium hydroxide on the flame-retardant properties of the nanocomposites. Significance: The resulting magnesium hydroxide nanoparticles not only retain the intrinsic merits of conventional magnesium hydroxide, including non-toxicity, smoke suppression, and environmental friendliness, but also serve as functional fillers capable of enhancing both the mechanical and flame-retardant properties of polymer matrices. Compared with traditional flame-retardant additives, these nanoparticles exhibit clear advantages, thereby demonstrating their high-performance characteristics. This work provides deep insights into ionic liquid-mediated crystal engineering and offers a sustainable pathway for designing high-performance nano flame retardants.

Urea is widely used in agriculture because of its high nitrogen content and low cost, but its utilization efficiency is often limited by volatilization, leaching, and nitrification-denitrification losses. In this study, sodium alginate (SA) was hydrophobically modified by free-radical grafting with methyl methacrylate (MMA) to obtain SA-PMMA, which was subsequently ionically cross-linked with chitosan (CS) to construct hydrogel carriers for controlled-release urea fertilizers. The resulting materials were characterized by FTIR, XRD, TG-DTG, XPS, and SEM-EDS, confirming successful grafting and indicating interactions between urea and the SA-PMMA/CS matrix. The effects of grafting ratio on water absorption, urea loading, nitrogen release, degradation, and fertilizer performance were systematically investigated. Among the five formulations, sample Z3 exhibited the best overall release behavior, with a cumulative nitrogen release of 77.33% over 56 days, meeting the national standard for slow-release fertilizers. Release-kinetic analysis showed that nitrogen release was best described by the first-order model and was governed by Fickian diffusion. In spinach pot experiments conducted at the same nitrogen input, the hydrogel fertilizers, especially Z3, promoted root development, leaf expansion, chlorophyll accumulation, dry matter production, and plant nitrogen uptake compared with conventional urea. These results demonstrate that hydrophobically modified SA/CS hydrogels are promising carriers for improving urea retention, regulating nitrogen release, and enhancing agricultural nitrogen-use efficiency.

Ammonium Polyphosphate (APP) is a novel water-soluble slow-release fertilizer. However, the current production cost of low water-soluble APP is relatively high. In this study, water-soluble APP was successfully prepared by using urea phosphate mother liquor as raw material and urea as a condenser through the processes of purification, concentration, drying, pulverization, and polymerization. Under the optimal conditions, the resulting product had a phosphorus pentoxide (P2O5) content of 51.70%, a total nitrogen content of 19.46%, a polymerization rate of 94.21% and an average polymerization degree of 3.79. XRD analysis confirmed that the product APP exhibited an amorphous structure. In addition, the prepared APP was applied in various soils, and the results indicated that APP could effectively reduce the pH value of alkaline soils. The available phosphorus content of alkaline soil is 22.75% and 29.46% higher than that of acidic soil, respectively. Acidity and high temperature will accelerate the hydrolysis of APP, resulting in more phosphorus being fixed by soil. The percentages of total nitrogen loss in urea, monoammonium phosphate (MAP), commercially available APP and self-made APP for forty days were 73.10%, 74.20%, 55.55% and 56.71%, respectively. APP can reduce nitrogen loss to a certain extent compared with traditional fertilizers. In general, the preparation of APP from urea phosphate mother liquor is conducive to the high-value utilization of urea phosphate mother liquor, and opens up a new way for low-cost preparation of APP.

[Objective]Surfactants affect the properties and controlled-release performance of coated fertilizers by influencing the structure of polyurethane film materials based on castor oil.This study offered a theoretical support for the practical use of surfactant-modified plant oil-based polyurethane coated urea in agriculture through a methodical examination of the properties of coated urea,surfactant-modified castor oil-based polyurethane film,and field tests.[Method]Using surfactant modification,castor oil-based polyurethane-coated urea(BPCU)was created.The surfactant modification mechanism was examined,and FT-IR was used to corroborate the polyurethane synthesis.The effects of surfactants on the hydrophobic properties of membrane materials were investigated.In Zhaodi Village,Xinxiang,Henan Province,a field experiment was carried out using homemade slow-release fertilizer to reduce fertilizer application by 20%while using regular urea as the control.The impact of BPCU on summer maize yield was examined,and Zhongjinyu 2513 was the test crop.[Result]By improving the compatibility of the polyurethane matrix and creating a pseudo-crosslinking effect,the surfactant could make the high hydroxyl value castor oil-based polyol and PM-200 more evenly distribution on the coating film's surface.Additionally,the cross-linking density was further enhanced by lowering the energy consumption of the interfacial reaction between the high hydroxyl value castor oil-based polyol and PM-200 to form polyurethane.The improved membrane material had a decreased residual carbon content,according to the results.The improved membrane shell's water contact angle was 105.5°,a 13.0%increase from the unmodified membrane shell's 93.4°.The modified membrane material had a 7-day water absorption rate of 1.64%,a porosity of 1.14%,and a swelling degree of 1.18%.The 7-day water absorption rate,porosity,and swelling degree were all reduced by 76.8%,76.7%,and 25.3%,respectively,when compared with the unmodified membrane material.The slow-release duration of BPCU was extended from 70 to 83 days at 0.5%surfactant addition,which was 18.6%longer than that of castor oil-based polyurethane-coated urea(PCU).With a 20%decrease and a 5%coating,the corn yield of the BPCU fertilizer was 11 908.1 kg·hm-2,a 22.0%increase over the maize yield of 9 757.2 kg·hm-2 following the application of regular urea.In contrast,the thousand-grain weight likewise rose by 16.9%.The yield and thousand-grain weight of maize were significantly impacted by the application of BPCU.It mostly influenced the thousand-grain weight of maize,which in turn impacted its yield.[Conclusion]It was demonstrated from aspects such as nitrogen release period and summer maize yield that the performance of BPCU was superior to that of the unmodified PCU.The application of BPCU could be regarded as an effective way to reduce fertilizer application and increase efficiency.The creation of novel coated controlled-release fertilizers was supported theoretically and technically by this study.

China is rich in phosphate rock (PR) resources, but there is a large amount of medium and low-grade PR. With rising phosphorus (P) demand in new energy and fertilizer industries, high-grade PR faces imminent depletion. Medium- and low-grade PR beneficiation is difficult and utilization complex. The process of directly converting medium-grade PR as raw material to produce superphosphate was developed by using the concentrated acid mineral powder method. The acidolysis law of PR powder and the influencing factors of the process were discussed. The effects of three factors, namely theoretical acid dosage, sulfuric acid concentration, reaction time, particle size, and acid temperature, on the performance of the product were investigated. The response surface optimization experiment was designed, and the results of the available P conversion rate and the interaction of each factor were obtained. The maximum predicted value of the response surface of the available P conversion rate of the experimental product, fresh superphosphate fertilizer, was 90.48%, and the measured value of the sample was 90.67%. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy emission spectrometer (SEM-EDS) characterization and analysis were conducted on the products after acidolysis. The acidolysis reaction of PR was complete, and the main components were Ca(H2PO4)2 & centerdot;H2O and CaSO4. The production process of traditional phosphate fertilizer has been simplified. The process is feasible and economical, opening up a new technical route for the efficient utilization of medium-grade PR.

Magnesium hydroxide (MH) synthesized via conventional methods suffers from critical drawbacks, including broad particle size distribution, severe agglomeration, and poor dispersibility in organic matrices. To address these challenges, this study used MgSO4 & sdot;7H2O and NaOH as raw materials, with 1-butyl-3-methylimidazolium acrylate (ILA, C11H18N2O2) and N-methylimidazolium acrylate (ILB, C7H10N2O2) as regulators. Homogeneous precipitation was successfully employed to synthesize nano-MH and its dispersion. Through rigorous optimization of the process, the optimal preparation parameters were precisely defined. Characterization results indicate that the addition of acrylic ionic liquids (ILs) can effectively decrease the particle size of nano-MH and enhance the stability of its dispersion. Under the regulation of two types of acrylic ILs, the average particle sizes of the MH dispersions are 93.96 nm and 154.50 nm, respectively. Moreover, density functional theory (DFT) simulations and calculations have unveiled the adsorption behaviors of different ILs on the MH (110) crystal plane. ILA exhibited a steric hindrance effect, with its cations interacting with the substrate and adsorbing onto the (110) crystal plane of MH. In contrast, ILB, characterized by its short-branched chains, enabled the simultaneous binding and adsorption of both anions and cations to the substrate on the (110) crystal plane. As a result, ILB not only formed hydrogen bonds but also established Mg-O ionic bonds with MH, thus showing a stronger adsorption affinity on the (110) crystal plane. These findings lay a solid theoretical foundation for the synthesis and application of nano-MH.

Currently, it is increasingly observed that the environment is being severely polluted due to the low fertilizer utilization rate and the volatilization of nitrogen (N) elements. In this study, industrial grade castor oil (CO) was used as a raw material to prepare film-coated urea with excellent slow release and control loss performance which can not only effectively alleviate the pollution caused by N elemental to the environment, but also provide a continuous source of nitrogen to the crops, and can reduce the amount of fertilizer applied while ensuring the yield to a certain extent. Experiments were carried out to obtain castor oil-based polyol (COP) with hydroxyl content of 247.45 mg KOH/g and viscosity of 692.1 mPa & sdot;s by ester exchange reaction, and then reacted with poly (methylene polyphenylene) isocyanate (PM-200) to obtain Polyurethane coated urea (PCU) with a good slowrelease effect, and the slow-release period of the PCU-2 could be up to 70 days. The outstanding inhibitory effect of PCU-2 on ammonia volatilization was confirmed by ammonia volatilization tests, with a reduction of 60 % observed compared to uncoated urea. Field experiments conducted in Lankao County, Henan Province, revealed that 20 % reduction of the fertilizer resulted in a 3.09 % increase in summer maize yield. The results suggest that increased grain production can be achieved by PCU while simultaneously protecting the environment.

Nano-magnesium hydroxide (MH), an environmentally friendly inorganic material, is widely used in flame retardancy, adsorption, and nanocomposites. However, precise control of its nanostructure and crystallization kinetics during synthesis remains a key challenge. This study aims to unveil the ionic liquid-mediated MH crystallization mechanism. MH was prepared via homogeneous precipitation using NaOH and MgSO4 & sdot;7H2O as raw materials, with two 1-butyl-3-methylimidazolium-based ILs (ILA, ILB) as regulators. Via a synergistic approach of crystallization kinetics analysis and density functional theory (DFT) simulation, this study elucidated how ionic liquids (ILs) regulate MH nucleation and growth. Real-time conductivity monitoring tracked Mg2+ dynamics, and the effects of temperature, reactant concentration, and IL type on MH crystallization kinetics were studied. DFT calculations optimized the precursor complexes (MgSO4-ILA/ILB), while electrostatic potential (ESP) and atom-in-molecule (AIM) analyses resolved the coordination between anions and Mg2+ as well as the regulatory mechanism of nucleophilic attack. Experiments show that under appropriate temperatures, ILs inhibit nucleation and induce smaller particles, with ILB more effective in growth control. ESP and frontier orbital analyses reveal IL cations affect growth kinetics and particle size through hydrogen bond-mediated nucleophilic attack direction and steric effects. This work reveals IL anions control MH crystallization via synergistic electrostatic, coordination, and steric effects, offering a framework for IL-based MH nanostructure customization.

At present, vegetable oil-based polyurethane still has the disadvantages of high cost and unsatisfactory loss control effect. Therefore, in this study, nano-copper-based modified castor oil-based polyurethane membrane was used to prepare modified polyurethane-coated urea to increase the slow-release effect of polyurethanecoated urea. The results showed that the water absorption, swelling and porosity degree of nano-copper-based modified polyurethane coated urea (HPCU) were the lowest when the addition amount of nano-copper laurate was 0.7 %, which were 3.31 %, 3.86 % and 0.97 %, respectively. In the case of 5 % coating amount unchanged, the sustained release period was extended from 70 days to 105 days. Compared with common urea, the ammonia volatilization of HPCU decreased by 87.83 %, and the nitrogen leaching decreased by 92.60 %. Field experiments of maize and wheat were conducted in Lankao, Yuzhou and Xinxiang counties of Henan Province. Compared with the common urea treatment group, the HPCU treatment group reduced the amount of fertilizer by 20 % for field experiments. Compared with common urea, the ammonia volatilization accumulation of HPCU in Lankao and Yuzhou for 13 days decreased by 10.03 % and 13.19 %, and the maize yield increased by 3.84 % and 4.38 %. The results of wheat field experiment in Xinxiang showed that compared with common urea (topdressing), the yield of wheat treated with HPCU increased by 14.34 % under topdressing condition and 13.65 % under no topdressing condition. The results of maize field experiment in Xinxiang showed that the yield of maize with HPCU was 11.10 % higher than that of ordinary urea.

In the present study, we successfully developed hydroxy-terminated polydimethylsiloxane (PDHT) and nanoSiO2 hydrophobic polyurethane-coated urea by applying the optimal conditions for hydrophobic polyurethane preparation. The hydrophobic polyurethane membrane material undergoes a comprehensive characterization. Infrared analysis confirmed the successful grafting of PDHT onto the polyurethane membrane material. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-Ray Spectroscopy (EDX) analysis verify the even distribution of silicon on the surface of the membrane material. By Scanning Electron Microscopy (SEM) comparison, we elucidate the micro-structural disparity between the unmodified and modified castor oil-based polyurethane, accounting for the micro-level performance enhancement. The resulting modified membrane exhibited a water contact angle of 133.6 degrees, indicative of its hydrophobic nature. The optimal ratios for PDHT and nano-SiO2 were determined to be 16 % and 2 %, respectively. Notably, hydrophobic polyurethane-coated urea demonstrated an extended-release period of 98 days (5 % coating amount), a 40 % improvement over its unmodified counterpart. In addition, the silicone-modified coated urea reduced the amount of ammonia volatilization by about 76.32 %, which plays a significant role in enhancing fertilizer utilization efficiency and is important for ecological environment protection. This research provides a straightforward and efficient way to fabricate slow-release fertilizers, with significant implications for the advancement of coated slow-release fertilizer technology.

It is a valid path to realize the zero discharge of coal chemical wastewater by using the fractional crystallization method to recycle the miscellaneous salt in high-salinity wastewater. In this study, the thermodynamics and nucleation kinetics of sodium chloride (NaCl) and sodium sulfate (Na2SO4) crystallization in coal chemical wastewater were systematically studied. Through analyses of solubility, metastable zone width, and induction period, it was found that the impurity dimethoxymethane would increase the solid–liquid interface energy and critical crystal size during the nucleation of Na2SO4. Ternary phase diagrams of the pseudo-ternary Na2SO4-NaCl-H2O systems in simulated wastewater were plotted in the temperature range of 303.15 to 333.15 K, indicating that a co-ionization effect existed between NaCl and Na2SO4, and NaCl had a strong salting out effect on Na2SO4. Finally, the nucleation rate and growth rate of Na2SO4 crystals under simulated wastewater conditions were determined by the intermittent dynamic method, and the crystallization kinetic models of Na2SO4 were established. The crystallization nucleation of Na2SO4 crystals was found to be secondary nucleation controlled by surface reactions. The basic theoretical research of crystallization in this study is expected to fundamentally promote the application of fractional crystallization to realize the resource utilization of high-salinity wastewater in the coal chemical industry.

A route for selective recovery of magnesium (Mg), iron (Fe), and silicon (Si) from blast-furnace magnesium slag was studied in this paper. The experimental results demonstrated that under favourable conditions, such as sulfuric acid concentrations of 6% weight in weight (w/w), solid-liquid ratio (S/L) of 1:30, temperatures of 80 degrees C, and a time of 30 min, the leaching rates of Mg, Si, and Fe can be reached up to 85.86%, 63.80%, and 17.04%, respectively. Flocculation desilication was used to remove Si up to 85.7% from the filtrate, and amorphous SiO2 was obtained with a purity of 95.8%. A significant level of effectiveness has been achieved in utilising ammonia neutralisation to eliminate iron (Fe) from the filtrate, with an impressive removal rate of 99.73%. Finally, a filtrate with a high concentration of magnesium (Mg) was obtained. Dans cet article, on a & eacute;tudi & eacute; une voie de r & eacute;cup & eacute;ration s & eacute;lective du magn & eacute;sium (Mg), du fer (Fe) et du silicium (Si) & agrave; partir des scories de magn & eacute;sium du haut fourneau. Les r & eacute;sultats exp & eacute;rimentaux ont d & eacute;montr & eacute; que dans des conditions favorables, telles que des concentrations en acide sulfurique de 6% en poids (p/p), un rapport solide-liquide (S/L) de 1:30, des temp & eacute;ratures de 80 degrees C et un temps de 30 min, les taux de lixiviation du Mg, Si et Fe peuvent atteindre jusqu'& agrave; 85.86%, 63.80% et 17.04%, respectivement. On a utilis & eacute; la d & eacute;silication par floculation pour & eacute;liminer jusqu'& agrave; 85.7% de Si du filtrat, et l'on a obtenu du SiO2 amorphe avec une puret & eacute; de 95.8%. On a obtenu un niveau d'efficacit & eacute; significatif en utilisant la neutralisation & agrave; l'ammoniac pour & eacute;liminer le fer (Fe) du filtrat, avec un taux d'& eacute;limination impressionnant de 99.73%. Enfin, l'on a obtenu un filtrat & agrave; forte concentration en magn & eacute;sium (Mg).

Effect of impurity silicon on the crystallization process of sodium zincate solution was studied. Based on the crystal phase and thermodynamics analysis, the influence mechanism of impurity silicon on the structure of sodium zincate solution was obtained. The decomposition behavior of sodium zincate solution was analyzed. The effects of impurity silicon concentration, crystal seed and temperature on the crystallization process of sodium zincate solution were investigated. The results show that there is a critical silicon concentration. When the silicon concentration is higher than the critical silicon concentration, the impurity silicon inhibits the crystallization process; when the silicon concentration is lower than the critical one, the impurity silicon promotes the crystallization process. When zinc oxide is used as crystal seed, the critical silicon concentration at 35, 50, and 60 celcius are in the range of 0.20-0.40, 0.054-0.20 and 0-0.054 g/L, respectively; when zinc hydroxide is used as crystal seed, the critical silicon concentration is in the range of 0.20-0.40 g/L at 35 celcius. The critical silicon concentration decreases with increasing temperature. When silicon content is low, the phase is & epsilon;-Zn(OH)2 of polyhedron; when silicon content is high, the phase is & gamma;-Zn(OH)2 of nanorods and cuboids. Increasing the temperature can inhibit the formation of & gamma;-Zn(OH)2. The presence of silicon impurities may reorganize the structure of sodium zincate solution, and is conducive to the existence of zinc ions in the form of Zn(OH)+. The increase of temperature can reduce the influence of silicon impurities.

Using phosphogypsum as raw material,the impurities in phosphogypsum were removed by water washing method,architectural gypsum was prepared by low-temperature calcination,and the effects of calcination temperature and calcina-tion time on gypsum strength and three-phase component content were studied with the help of DSC-TG technology,and then the effects of additives such as sodium tripolyphosphate,fly ash reinforcing agent,melamine and polypropylene fiber of retarder were investigated on the physical and chemical properties of gypsum test block.The results showed that the mass fraction of β-CaSO4·0.5H2O prepared under the condition of low calcination at 170℃and 3 h was 72.23%,and the me-chanical properties of gypsum test block were better than those of grade 2.0 products in GB/T 9776-2008"Building Gyp-sum"The sodium tripolyphosphate with an added amount of 0.15%(mass fraction,the same below)was used as a retarder,and fly ash with an added amount of 5.00%was used as a reinforcing agent with an addition amount of 0.05%melamine was used as a water reducing agent and polypropylene fiber with an addition of 1.00%was modified to build gypsum powder,and the dry flexural strength and dry compressive strength of the prepared gypsum test block were 4.17 MPa and 12.97 MPa for 7 d.The role of various additives in the preparation of architectural gypsum powder using phosphogypsum as raw material was discussed,and the construction gypsum powder with good performance was prepared,which provided technical meth-ods and theoretical basis for the comprehensive utilization of phosphogypsum.

Abstract Ammonium polyphosphate (APP) is rich in nitrogen (N) and phosphorus (P), which is a raw material for the high-efficiency water-soluble fertilizer production. In this work, the water-soluble APP was directly synthesized using commercial grade-urea phosphate and urea in a microwave reactor. The effects of the molar ratio of urea to phosphate urea (UP), microwave power and reaction time on the quality of APP were also studied. Single-factor experiments indicate that with the optimal conditions: the molar ratio of 0.4, the microwave power of 720 W, and the reaction time of 9 min, the average polymerization degree of APP was 18.91, and the solubility was 6.31 g/100 g H2O. Orthogonal experiment indicates that the order of significant factors for APP production is molar ratio > reaction time > microwave power. Based on the results of the range analysis and analysis of variance, the optimized conditions were found at the molar ratio of 0.6, the microwave power of 720 W, and the reaction time of 9 min, the average polymerization degree of the APP was 21.7 and the solubility was 6.03 g/100 g H2O at 25 °C. The TGA analysis showed that the synthesized APP had a good thermal stability. Its XRD spectrum was the same as the crystalline form I.

The crystallization of zinc oxide from sodium zincate solution is the key step in the process for treating zinc oxide mineral ores and residues by NaOH method. The crystallization kinetics including nucleation, growth and aggregation was investigated in a batch crystallizer. It was found that zinc hydroxide could be converted into zinc oxide under hydrothermal conditions without calcinations. Effects of temperature, seed, supersaturation and agitation speed on the crystallization were studied. The main structure of zincate changed with varied temperature. Zinc oxide particles were spherical particles formed by agglomeration of zinc oxide nanorods. The growth rate, the nucleation rate and the aggregation kernel were calculated by moments analysis based on the particle size distribution. The volume growth mechanism and linear growth mechanism of zinc oxide were controlled by diffusion process and surface reaction. In batch crystallization, the nucleation rate decreased with the increase of suspension density but increased with the increase of agitation rate. The reaction time had the most significant effect on the agglomeration factor. The agglomeration between zinc oxide particles could be improved by increasing the particle collision frequency.