Nanofiltration (NF) is considered a competitive purification method for acidic stream treatments. However, conventional thin-film composite NF membranes degrade under acid exposures, limiting their applications in industrial acid treatment. For example, wet-process phosphoric acid contains impurities of multivalent metal ions, but NF membrane technologies for impurity removal under harsh conditions are still immature. In this work, we develop a novel strategy of acid-resistant nanofiltration membranes based on interfacial polymerization (IP) of polyethyleneimine (PEI) and cyanuric chloride (CC) with the s-triazine ring. The IP process was optimized by orthogonal experiments to obtain positively charged PEI-CC membranes with a molecular weight cut-off (MWCO) of 337 Da. We further applied it to the approximate industrial phosphoric acid purification condition. In the tests using a mixed solution containing 20 wt% P2O5, 2 g/L Fe3+, 2 g/L Al3+, and 2 g/L Mg2+ at 0.7 MPa and 25 °C, the NF membrane achieved 56% rejection of Fe, Al, and Mg and over 97% permeation of phosphorus. In addition, the PEI-CC membrane exhibited excellent acid resistance in the 48 h dynamic acid permeation experiment. The simple fabrication procedure of PEI-CC membrane has excellent acid resistance and great potential for industrial applications.

Conventional wet process phosphoric acid production of crude phosphoric acid contains many impurities.A cost-effective and environmentally friendly method for removing impurity ions is necessary.Although nanofiltration membranes have been widely used in water treatment,there are few studies on removing metal ions in acidic systems,especially phos-phoric acid systems.The separation performance of five nanofiltration membranes in phosphoric acid was investigated.The results indicated that the rejections of nanofiltration membranes was decreased to varying degrees with increasing concentra-tions of phosphoric acid and temperature.The materials of the selective separation layer had a significant impact on the sepa-ration performance of nanofiltration membranes in phosphoric acid.The interaction of multiple mechanisms,including steric hindrance,dielectric repulsion,and Donnan repulsion,affected the separation efficiency of nanofiltration membranes.Among the investigated commercial membranes,NF4 exhibited the least susceptibility to variations in phosphoric acid con-centration and temperature,while demonstrating excellent acid stability.At 30℃,the average rejections of Fe3+,Al3+ and Mg2+ in a phosphoric acid solution of 20%P2O5 by NF4 were more significant than 84.83%,but the rejection of P was less than 5%,which showed an excellent prospect for application in phosphoric acid purification.

To obtain the high-quality basic magnesium sulfate whiskers,magnesium hydroxide and magnesium sulfate hep-tahydrate were used to prepare basic magnesium sulfate whiskers with the hydrothermal method.The influences of hydrother-mal parameters on whisker morphology were investigated,which included the molar ratio of magnesium sulfate heptahydrate to magnesium hydroxide,hydrothermal time,stirring speed,addition amount of magnesium sulfate heptahydrate,and hydro-thermal temperature.The whisker products were characterized by the various instruments of X-ray diffractometry(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),selected area electron diffraction(SAED),and Fourier-transform infrared spectrum(FT-IR).The results showed that the optimized process parameters were as follow-ing:the molar ratio of magnesium sulfate heptahydrate to magnesium hydroxide was 3∶1,hydrothermal time was 2 h,stirring speed was 400 r/min,addition amount of magnesium sulfate heptahydrate was 4.93 g,hydrothermal temperature was 180℃and the reaction medium of water was 80 mL.The products synthesized at the optimized conditions were mainly fibrous whis-kers.The aspect ratio of fibrous whisker was more than 160 with the diameter of 300～500 nm and the length of 80～100 μm.Therefore,the optimization of the process parameters could effectively improve the dispersion and aspect ratio of basic mag-nesium sulfate whiskers.

A new extractant PN-1 was synthesized, and an ultrasound-assisted micro-channel extraction (UAME) system was developed for the extraction of magnesium from wet-process phosphoric acid ( WPA). The effects of O/A ratio, P2O5 content, initial pH, ultrasound power, and aqueous phase ratio on extraction were investigated. The extraction efficiency of Mg2+ could reach 89.09% under the conditions of 74 W ultrasound power, 4 O/A ratio, and 0.2 mL/min aqueous phase velocity. The response surface methodology (RSM) result indicated that O/A ratio and aqueous phase velocity have extremely significant influences on extraction efficiency, significant interaction existed between ultrasound power and aqueous phase velocity, and ultrasound power evidently reduced extraction time. Furthermore, the magnesium could be fully stripped by 1 mol/L H2SO4 with a phase ratio lower than 2. Thus, the new extractant PN-1 and ultrasound-assisted microchannel extraction system are suitable for the extraction of magnesium from wet-process phosphoric acid.

In this study, a new type of ammonium polyphosphate-intercalated organic montmorillonite (APP/OMt) was synthesized using in-situ polymerization, and the chemical structure and surface morphology of APP/OMt was confirmed by FT-IR, XRD, EDS and SEM. Moreover, the intumescent flame retardant (IFR) composed of APP/OMt, pentaerythritol (PER) and melamine (MA) was added into polypropylene (PP) to fabricate the PP/IFRAPP/OMt composites, and their flame-retardant and mechanical properties were characterized systematically. When the additive mass of the flame retardants was 30 %, the limiting oxygen index (LOI) value reached 33.3 %, and the UL-94 test passed the V-0 level when the added amount was only 20 %. Especially, compared to the counterpart of IFRAPP, the addition of IFRAPP/OMt dramatically decreased the released smoke of PP during combustion, and the quality of carbon layer after combustion was obviously improved. The flame-retardant mechanism of IFRAPP/OMt was deeply explored. In addition, the mechanical properties of PP composites with IFRAPP/OMt were significantly improved compared with IFRAPP. The enhanced flame retardancy and mechanical strength were attributed to the synergistic effect between OMt and IFR particles along with improved the dispersion of IFRAPP/OMt within the PP matrix.

The decomposition reaction of phosphate rock under the action of microwave plasma was investigated. Phosphate rock and its decomposition products were characterized by x-ray diffraction (XRD), energy disperse spectroscopy (EDS), and chemical analysis. The measurements of electron temperature (T e) and electron density (N e) of plasma plume under atmospheric pressure were carried out using optical emission spectroscopy(OES). The electron temperature (T e) was determined based on the calculation of the relative intensity of the O II (301.91 nm) and O II (347.49 nm) spectral lines. Correspondingly, electron densities were obtained using the Saha ionization equation which was based on the C I (247.86 nm) line and the C II (296.62 nm) line under the assumption of local thermodynamic equilibrium (LTE). The relationship between the relative intensity of the active components and the gas output was studied by the spectrometer. Finally the reaction mechanism of the decomposition of the phosphate rock under the action of the atmospheric pressure microwave plasma was proposed. The results showed that with the increase of CO flow and microwave power, the electron temperature and electron density in the plasma show a decreasing and increasing trend. The CO is dissociated into gaseous carbon ions under the action of microwave plasma, and the presence of gaseous carbon ions promotes the decomposition of the phosphate rock.

气体经过等离子体活化后具有很高的化学活性,可以加快化学反应速率.本实验利用微波产生的CO等离子体还原CaSO4,结果表明,激发态CO含量是影响反应速率的重要因素,在CO流量为0.6 L/min,微波输入功率为1350W下,反应温度为875℃,反应12 min,转化率就可达86.01％.

In the present study, different ratios of layered double hydroxides (LDHs) were synthesized via co-precipitation method. The synthesized LDHs were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), nitrogen adsorption-desorption analysis, point of zero charges (pHpzc), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Phosphate adsorption performances were estimated by batch adsorption experiments; desorption hysteresis and adsorption mechanism were also investigated. The XRD, SEM and TEM results confirmed the multilayer structure of the synthesized LDHs. The pseudo-second-order kinetic model and the Freundlich model describe the adsorption behavior of LDHs best. The maximum adsorption capacity is 185.86 mg-KH2PO4/g for Mg2Al-NO3 LDH. When the dosage of LDHs was greater than 2 g/L, the phosphorus content in the solution decreased from 30 mg-P/L to 0.077 mg-P/L after adsorption by Mg2Al-NO3 LDH. All the results reveal that Mg2Al-NO3 LDH is a potential adsorbent for removing phosphate from aqueous solution.

Depletion of phosphate ore is one of the important resource crises in the world. The exploration of the transfer regularity of mineral impurities to liquid in the digestion process of phosphate rock is of great significance to the production of agricultural fertilizer. In this paper, the reaction kinetics experiments of iron and aluminum compounds in phosphate ore particles were carried out in the range of temperature 50-70 degrees and phosphoric acid concentration 15-25%. Under the combined temperature and concentration conditions, a large number of experiments were carried out to determine the conversion fraction of impurities, and the relationship between conversion fraction and time was obtained. A novel phenomenon of liquid-solid two-phase reaction kinetics was discovered. That is the negative temperature effect. When acid concentration is higher than the critical point, the reaction conversion fraction increases with increasing temperature, but it decreases with increasing temperature below the critical value. It has been found that this phenomenon is caused by the mutual coupling of the phase transition, mass transfer and chemical reaction in the micro-pores structure, as well as specific solubility characteristics of iron-aluminum phosphate. According to the mechanism analysis, the kinetic model was established, which is in good agreement with the experimental data. It can be used to predict the reaction behavior of iron and aluminum mineral impurities of phosphate rock in phosphoric acid. And the kinetics parameters such as D-pd, gamma, D-cop were thus obtained. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

从人类世来临的观点出发,概括了中国近年来无机固体废弃物处理的重要性和技术进展.按照中国无机固体废弃物的化学组成和加工特点,可以将其分为硅钙型、硅铝型、石膏型、钙镁型和复合型等几大类.介绍了相关固体废弃物的现状、处理技术进展及研究情况.展望了固体废弃物处理的技术发展方向,可为从事相关工作的技术人员提供参考.

An ultrasonic assisted microchannel extraction (UAME) method was developed for the extraction of Fe(III) from wet-process phosphoric acid with di(2-ethylhexyl)phosphoric acid (D2EHPA). The influences of ultrasonic power, extractant concentration, water phase velocity and the ratio of the organic and aqueous phases (O/A) on the extraction rate of Fe(III) were systematically studied. The results showed that the extraction efficiency of Fe(III) reached 91.08%, which was significantly higher than that for ultrasound extraction and microchannel extraction respectively. Response surface methodology was adopted to obtain the optimal conditions and to evaluate the significance of variables affecting the extraction efficiency. The extraction efficiency of Fe(III) reached 92.24% under the following optimum conditions: extractant concentration, 2.1 mol/L; aqueous phase velocity, 0.055 mL/min; ratio of organic phase and aqueous phase, 2.98.

为了确定反胶团二壬基萘磺酸萃取水相中Mg2+的过程机理,以二壬基萘磺酸为萃取剂、磺化煤油为稀释剂所组成的反胶团有机相对水中的Mg2+进行了萃取研究.考察了反胶团的皂化率、水相中镁盐阴离子种类等对萃取率的影响,同时考察了萃取温度、水相中pH值对分配比的影响,萃取饱和容量随萃取剂浓度的变化情况以及Mg2+在两相中的分配情况.研究结果显示,反胶团的皂化率、水相中镁盐阴离子种类对萃取过程无明显影响;萃取分配比随萃取温度的升高而增大;在萃取体系中水相pH值低于4时,分配比随pH值的增加而增大,pH值大于4后,分配比变化幅度较小;萃取饱和容量随萃取剂浓度的增加而增大,且与萃取剂浓度呈线性关系.二壬基萘磺酸从水相介质中萃取Mg2+的过程是吸热反应,其萃取过程热效应(ΔH)为5.135kJ/mol.研究表明,反胶团二壬基萘磺酸萃取Mg2+的过程为阳离子交换,这一研究结果为二壬基萘磺酸从冶金废水中萃取回收镁提供了理论基础和借鉴.

研究了磷酸三丁酯(TBP)、正癸醇(Decanol)复合萃取剂对盐酸介质中钛的萃取性能.研究结果表明,盐酸介质中钛的萃取率随磷酸三丁酯、正癸醇和氯离子浓度的增加而增加.萃取低浓度钛时钛在有机相中以TiCl4(TBP)2Decanol的形式存在,萃取高浓度钛时以TiCl4TBP(Decanol)1/2的形式存在.萃取有机相的粒度测定、电导测定、红外光谱分析和协同萃取研究结果表明,在高浓度钛的萃取过程中形成反胶团,即磷酸三丁酯—正癸醇对盐酸介质中高浓度钛的萃取以溶剂萃取和反胶团萃取相结合的方式进行.萃取速率很快,10 min内达萃取平衡.同时,磷酸三丁酯、正癸醇复合萃取剂对盐酸介质中的钙、镁、铝离子无萃取.绘制了复合萃取剂对8 mol·L-1盐酸介质中钛的萃取等温线,考察了逆流萃取过程级数.

采用共沉淀法合成了镁铝水滑石,考察了镁铝比、沉淀剂用量、反应时间、搅拌速率、焙烧温度等对镁铝水滑石吸附磷性能的影响.实验结果表明:Mg/Al-LDH对水中的磷具有良好的吸附作用.其最佳制备条件为:Mg/Al摩尔比3∶1、沉淀剂用量[16OH-+CO32-]/[6Mg2++2A13+]摩尔比1∶1、反应时间3h、搅拌速度300 r·min-1.当吸附剂用量为0.3g,水中磷的吸附率可达到100％.经过500℃焙烧3h,吸附剂用量0.1g时,吸附率比未焙烧的水滑石提高了18％.使用X射线衍射(XRD)、红外光谱(FT-IR)、比表面积及孔径分析仪(BET)等手段对镁铝水滑石的结构进行了表征.并对其吸附动力学进行了研究,其吸附动力学表现为假二级动力学.

In order to improve titanium (IV) extraction efficiency from hydrochloric acid solution, kinetics of titanium (IV) extraction from hydrochloric acid solution with tributylphosphate (TBP) and decanol in kerosene was investigated (using a Lewis cell based on reverse micelle extraction). Effects of stirring speed, temperature, interfacial area and reactant concentration were discussed. The results show that the extraction speed increases with the increase of stirring speed, interfacial area, temperature, extractant concentration, titanium (IV) concentration and chloride ion concentration. The activation energy of extraction is 31.73 kJ?mol-1, and the process is controlled by both diffusion in aqueous phase and reaction. The kinetic equation of titanium (IV) extraction from hydrochloric acid solution with TBP and decanol is obtained.

对磷酸浸取含稀土磷矿得到的酸解溶液中稀土萃取回收进行研究.通过对萃取剂的选择,萃取和反萃条件的试验优化选取,从脱钙后得到的粗磷酸中利用萃取剂P204进行萃取,当相比为2:1,P204浓度2 mol/L时,经过六级萃取后,萃取率达到97.13%.在相比O/A=1:1,以6 mol/L HCl进行反萃时,一级反萃率可达到50%以上,采用六级可达近90%.

An ultrasound-assisted extraction (UAE) method was developed for the extraction of Fe (III) from wet-process phosphoric acid with di (2-ethylhexyl) phosphoric acid (D2EHPA). The influences of UAE parameters, including ultrasonic power, extraction time, concentration of D2EHPA and extraction temperature, were systematically studied. The response surface methodology, a statistical technique, was used to obtain the optimal conditions and evaluate the significance of variables affecting the extraction efficiency of the UAE. It was found that ultrasound could markedly improve the extraction rate of Fe (III) with D2EHPA, the largest improvement is up to 7 times compared with the traditional solvent extraction method. However, the extraction equilibrium of the extraction system was not affected by ultrasound. It is believed that the cavitation effect of ultrasound, along with the increased interfacial surface area, contribute to the enhancement of the extraction rate.

农用聚磷酸铵在中国的发展和研究起步较晚,因此有必要对其生产技术做深入的研究.对磷酸法、磷酸尿素缩合法制备农用聚磷酸铵做了研究,考察了反应温度、反应时间、初始磷酸浓度、反应物料配比等对产品性质的影响.研究表明,当磷酸中P2O5质量分数为50％、聚合温度为240℃、聚合时间为180 min时,磷酸法所制备的产品聚合度可以达到14.9;尿素对聚磷酸铵的聚合度具有显著影响,若聚合温度为240℃、磷酸中P2O5质量分数为50％条件下引入与磷酸物质的量比为1.4的尿素反应120 rmin,可制得聚合度为31.5的Ⅰ型聚磷酸铵.

The structural and mechanical properties of ZnS in both B3 and B1 phases have been investigated by the generalized gradient approximation (GGA) within the plane-wave pseudopotential density functional theory (DFT). The obtained lattice parameters and bulk modulus of ZnS for both B3 and B1 structures are well in line with the available theoretical and experimental results. Using the enthalpy–pressure data, we have predicted that the phase transition pressure of ZnS from B3 to B1 is 17.26 GPa, which is in good agreement with previous experimental values. The hydrostatic pressure-dependent elastic properties of the two structures, such as bulk modulus, shear modulus and Young’s modulus, are discussed. Then, the mechanical characteristics of ZnS, including ductile/brittle behavior and elastic anisotropy of the two cubic single-crystal structures, are investigated in details. Furthermore, the thermodynamic properties of ZnS under extreme condition are explored by quasi-harmonic Debye modeling. The calculated results show that the ductility and elastic anisotropy increase with pressure clearly except the ductility of B1. Besides, the temperature and pressure dependencies of the heat capacity and the Debye temperature are obtained and analyzed in the wide ranges.

First-principles calculations of the electronic structure and thermodynamic properties of calcium sulfide (CaS) have been carried out by the plane-wave pseudopotential density functional theory method. The calculated values of lattice constant, elastic modulus and its derivative for CaS under zero pressure and zero temperature, agree well with the experimental data and some of the existing model calculations. The band structure and density of states are discussed in detail. Moreover, the dependences of the volume variation, bulk elastic modulus, thermal expansion coefficient and heat capacity on pressure have been investigated for the first time, so far as we know. It is concluded that under the condition of zero temperature (0 K) and zero pressure (0 GPa), the volume is 44.6 3 when the energy of the crystal unit cell reaches a minimum in the structural model of CaS, which is the most stable system. The energy band of CaS is mainly composed of low band gap, valence band and conduction band, the GV-XC band gap of CaS is 2.435 eV. The DOS results show that the valence band is mainly of Ca 3s and S 3p, while the conduction band is mainly of Ca 4d and a small amount of S 3p. At a certain temperature, the volume change rate, heat capacity and thermal expansion coefficient decrease with rising pressure, and the body elastic modulus B increases simultaneously. In contrast, when the pressure is constant, the volume change rate and body elastic modulus B decrease with the increase of temperature, while the thermal expansion coefficient and heat capacity increase as the temperature rises. When the temperature is higher than a certain value, the heat capacity CV is close to the Dulong-Petit limit, and the effect of temperature on the heat capacity is minimal. Furthermore, under the condition of low pressures, the influence of temperature on thermal expansion coefficient is greater than that of the pressure on it.