Phosphoric acid activation is currently the main method for industrial production of biomass-based activated car-bon,but the higher ash content limits its application in high-end fields such as medicine and food.Based on this,the effect of activation conditions(temperature,time,etc.)and washing conditions(medium,acid concentration,temperature,etc.)on the ash content and properties of activated carbon was investigated by using wet phosphoric acid as the activator and waste wood chips as the carbon source,and the surface properties and microstructure of activated carbon were analyzed by using TG,FT-IR,XRD,SEM and TEM characterization.The results showed that insoluble phosphate was the main factor in the generation of activated carbon ash,and that the activated carbon ash,iodine and methylene blue values could be regulated by controlling the activated carbon preparation process and washing process.The optimal process conditions were activation temperature of 500℃,phosphoric acid concentration of 70%,acid to chip ratio of 2∶1,activation time of 60 min,N2 protec-tion,washing solution dosage of 100 mL,washing solution concentration of 20%,washing medium of H3PO4,washing tem-perature of 80℃and washing time of 60 min.The activated carbon prepared under these conditions had an ash content of 1.07%,iodine value of 1 241.4 mg/g,methylene blue value of 285 mg/g,specific surface area of 2 290 m2/g,indicating that the activated carbon prepared by this technology had the potential to be applied in high-end industries such as food and medicine.
Fluorite tailings-based lightweight high-strength ceramsite was prepared by sintering with fluorite tailings and clay as raw materials and silicon carbide（SiC） as foaming agent. The effects of the amount of fluorite tailings,sintering temperature,sintering duration and SiC external dosage on the properties of ceramsite were systematically investi-gated. The crystal phase and microstructure of the obtained ceramsite samples were also analyzed by thermodynamic calculation,X-ray diffraction spectrum,scanning electron microscope and other detection methods. The results showed that when the proportion of fluorite tailings was 70%（mass fraction）,the proportion of clay was 30%（mass fraction）,the external proportion of SiC was 0.5%（mass fraction）,the preheating temperature was 450 ℃,the preheating time was 15 min,the sintering temperature as 1 210 ℃,the sintering time was 30 min,and the heating rate was 5 ℃/min,the fracturing force of the obtained fluorite tailings ceramisite was 527.9 N,the apparent density was 0.89 g/cm3,the water absorption rate was 0.21% in 1 h,and the cylinder compressive strength was 4.63 MPa,the bulk density was 594.6 kg/m3,which met the requirements of Grade 600 high-strength ceramsite for lightweight aggregates in GB/T 17431.1—2010“Lightweight Aggregates and Experimental Methods”.The research results could provide a new method for the resource utilization of fluorite tailings.
Propylene is an important industrial raw material mainly used in the production of polypropylene,acrylonitrile,isopropyl alcohol,acetone and propylene oxide.With the increasing demand for propylene,the technology of propane dehy-drogenation has been widely used in the industrial production of propylene.Although platinum-based and chromium-based catalysts have high activity in propane dehydrogenation,they are also prone to poisoning and deactivation.Metal oxides have attracted widespread attention as alternative non-precious metal catalysts.Firstly,the reaction pathway and deactivation mechanism of propane dehydrogenation catalyzed by metal oxides were introduced.It was pointed out that enhancing the C—H activation ability,alleviating the reconstruction and reduction of active components were the key to improving the pro-pane dehydrogenation performance of metal oxide catalysts.Then,several representative metal oxide catalysts were reviewed in detail,the mechanism of action and active species of various catalysts were summarized,and the existing problems of cor-responding catalysts were analyzed and discussed.Finally,key research directions for future propane dehydrogenation cata-lysts were proposed,which was expected to provide new ideas for the direct production of chemicals through the activation of low-carbon alkanes.
The effects of initial digestion water temperature,stirring speed,water-ash mass ratio and pressurized digestion on the morphological structure,particle size and specific surface area of the reaction product calcium hydroxide were inves-tigated by using industrial grade quicklime as raw materials,and the product calcium hydroxide was characterized by Mal-vern laser particle size distribution instrument,scanning electron microscope(SEM)and specific surface area analyzer.The results showed that the digestion rate was accelerated with the increase of the initial temperature of water,and when the stir-ring speed was 500 r/min,the initial temperature of water was 45～80℃,and the mass ratio of water to ash was 4∶1,the pro-duced calcium hydroxide had the narrowest particle size distribution and the maximum specific surface area was 18.23 m2/g.When the initial temperature of digested water was 25～45℃,the morphology of the product calcium hydroxide showed a"dendritic"shape,and when the initial temperature of the digestion water was 65～80℃,the shape of product calcium hy-droxide grew into"granular".The pressurized digestion method could obtain a large specific surface area of calcium hydrox-ide and its shape was"petal-like",and the maximum specific surface area was 29.32 m2/g.
The effect of pre-reduction treatment by adding aluminum powder to titanium oxysulfate solution containing mag-nesium,aluminum,and iron impurities and changing the valence of some elements on the process of iron removal from tita-nium liquid by hydrothermal hydrolysis was investigated.Under the guidance of electrode potential theory,all Fe(Ⅲ)in tita-nium liquid was reduced to Fe(Ⅱ),and a small amount of Ti(Ⅳ)was reduced to Ti(Ⅲ).Subsequently,hydrothermal reac-tion was conducted at 120℃for 4 h.Titanium hydrolysis efficiency of samples with and without pre-reduction were 98.59%and 97.47%,and iron content in the hydrolysate was 115 mg/kg and 11 710 mg/kg(based on TiO2),respectively.Combining the thermodynamic equilibrium constant of each reaction at 110～150℃with the relevant equilibrium equation,the concen-tration of each component in the equilibrium system at different temperatures was obtained by Newton-Raphson iterative method,and the change law of Mg,Al and Fe impurities in the solution with and without pre-reduction during the hydrother-mal hydrolysis process was illustrated.The strengthening mechanism of pre-reduction on the deferrization in the hydrother-mal hydrolysis process of titanium sulfate solution containing impurities was revealed through mutual verification of experi-ments and thermodynamics.
Removal of carbon impurities from trichlorosilane(SiHCl3)can improve the purity of polysilicon.However,the points of chlorodimethylsilane[(CH3)2SiHCl]and SiHCl3 are very close,and azeotrope is easily formed in the distillation process.Therefore,(CH3)2SiHCl in SiHCl3 is difficult to remove.It was proposed to use Cl2 as the chlorine source to convert(CH3)2SiHCl into high boiling methyl chlorosilane through thermal chlorination reaction to increase the relative volatility and facilitate the distillation.However,SiHCl3 and(CH3)2SiHCl were chlorinated at same time.Therefore,the change of the conversion of the two with temperature was investigated.The results showed that the conversions of(CH3)2SiHCl and SiHCl3 were 53.1%and 14.3%at 60℃and 120 min,and the selectivity of(CH3)2SiHCl was the best.Finally,the reaction path was calculated and analyzed by density functional theory,and the reaction mechanism was determined.The difference between the reactions of SiHCl3 and(CH3)2SiHCl resulted from the different energy barriers for the reactions of the SiCl3·and(CH3)2SiCl·radicals with Cl2.The energy barrier of the reaction of SiCl3·with Cl2 was 60.4 kJ/mol higher than that of the re-action of(CH3)2SiCl·.
Zinc chloride activated carbon(ZnAC)with optimal methylene blue(MB)adsorption performance was prepared from corn cob of Ningxia agricultural waste.Based on these conditions,zinc chloride and water vapor were used to prepare activated carbon(ZnHAC)at different activation temperatures.The structure and surface properties of ZnAC and ZnHAC were analyzed by BET,XRD,FT-IR,and SEM to elucidate the activation mechanism.The results showed that the optimum conditions for ZnCl2 activation were temperature of 500℃,activation time of 1 h,and zinc feed mass ratio of 1.5∶1.The spe-cific surface area of activated carbon was 2 299.75 m2/g,the cumulative pore volume was 1.28 cm3/g,and the adsorption ca-pacity of MB was 531.56 mg/g.The mesoporous rate of the activated carbon was up to more than 95%,and the mesoporous rate was increased with the increase in temperature,indicating that increasing temperature was conducive to the formation of mesoporous.At the same temperature,compared with ZnACT-1.5-1,the specific surface area and pore volume of Zn-HACT-1.5-1 increased significantly after water vapor was introduced,and the specific surface area of ZnHAC800-1.5-1 was in-creased by 349 m2/g compared with ZnAC800-1.5-1,and mesoporous pore volume,total pore volume,and pore size were nearly doubled,respectively.ZnHAC800-1.5-1 activated carbon surface contained more amorphous carbon.The activation effect of wa-ter vapor at high temperatures was more pronounced.The vapor made the activation effect more significant,because of en-riching the structure of activated carbon and the oxygen-containing functional groups on the surface of activated carbon,and increasing of the disordered degree of carbon structure.
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.
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.
Polyvinyl formal(PVFM)sponge supported Co-B/PVFM catalyst was prepared by impregnation-reduction method,and the effects of sodium borohydride concentration,sodium hydroxide concentration and reaction temperature on the catalytic hydrolysis of sodium borohydride were investigated.The results showed that the hydrogen production rate was increased with the increase of sodium borohydride concentration and reaction temperature,and with the increase of sodium hydroxide concentration,the hydrogen production rate was firstly increased and then decreased.The activation energy of the hydrolysis reaction was 29.02 kJ/mol.In the continuous reactor,Co-B/PVFM catalyst could catalyze hydrolysis of sodium bo-rohydride to produce hydrogen at a rate of 12.0 L/min,which could supply hydrogen for 1 kW fuel cell,and the catalytic ac-tivity did not decay for 100 min,showing great practical application potential.
In order to develop a more simple and efficient method of alumina modified cathode materials,and improve the rate and cycle performance of lithium battery cathode materials,the preparation of nano-alumina slurry with Ammonium polyacrylate(PAANH4)as dispersant and the coating of nano-alumina on the cathode material LiNi0.8Co0.1Mn0.1O2 were stud-ied.Through the experiment,it was optimized that the particle size of nano-alumina was smaller and uniform,when the addi-tion amount of PAANH4 was 4%,and the milling time was 8 h.This nano-alumina slurry was used to modify the cathode ma-terial of lithium ion battery.It was found that the addition of alumina did not change the surface morphology,particle size and crystal structure of the cathode material.In the electrochemical performance test,when the alumina coating amount was 0.3%(mass fraction),better enhanced rate performance was obtained,and when the alumina coating amount was 0.5%(mass fraction),better cycling stability was obtained.At 1C rate,the capacity retention rates of uncoated and 0.5%(mass fraction)alumina-coated cathode materials were 75.61%and 84.93%after 100 times,respectively.
The development of non chromium catalysts in the process of preparing 2-propylheptanol from aldehyde hydroge-nation is the key to achieving the greening of the process.The adsorption and diffusion characteristics of the mixed solution of 2-propylheptenal and 2-propylheptanol for copper silicon,copper chromium,and copper zinc aluminum three different copper-based composite oxides were investigated by adsorption diffusion method.And combined the structural characteris-tics of three different copper-based composite oxides,it was coupled with the hydrogenation performance of 2-propylhep-tenal in liquid phase.The results showed that 2-propylheptaneal adsorbed preferentially by copper silicon composite oxides at all concentration ranges,however,for copper-zinc and copper-chromium composite oxides,2-propylheptaneal adsorbed preferentially only while the mass fraction of 2-propylheptenal in the mixed solution was higher than 4.6%and 4.1%re-spectively.The adsorption selectivity,diffusion coefficient,and hydrogenation performance for 2-propylheptylenal of copper chromium composite oxide were optimal in liquid phase.
In order to explore the complex thermal process in the pyrolysis furnace,the core equipment of MgCl2 spray py-rolysis process,and improve the quality of process products and equipment service life,Euler-Lagrange method was used to establish a mathematical model of gas-particle two-phase flow heat transfer coupled with pyrolysis reaction.The temperature field,particle decomposition process and HCl distribution during the stable operation of pyrolysis furnace were studied.And the influence of gas inlet temperature and flow rate on MgO conversion and HCl distribution was explored.The results showed that the product conversion rate was gradually increased with the increase of flue gas inlet temperature and inlet flow in the scope of the study.When the flue gas inlet was kept at 1.5 m3/s,the product conversion rate reaches 100%at the inlet temperature of 1 423 K.When the flue gas inlet temperature was kept at 1 273 K,the product conversion rate reaches 100%at the inlet flow rate of 2.25 m3/s.As the particles moving downward,the HCl concentration was radually increased and reached a maximum concentration of 6.5%at the discharge port.Moreover,with the increase of flue gas inlet tempera-ture and inlet flow,the HCl concentration at the discharge port showed a change law of firstly increasing and then decreas-ing.The flue gas inlet temperature and inlet flow rate corresponding to the maximum value were 1 373 K and 1.75 m3/s,re-spectively.
Hexavalent chromium is commonly used in traditional chromium electrodeposition process,which can produce toxic acid fog and other polluting substances,resulting in environmental pollution.Compared with hexavalent chromium,tri-valent chromium electrodeposition technology has the advantages of lower energy consumption,less toxicity and less pollu-tion,so it has a long term application prospect.Due to the different ion deposition modes in different bath systems,the elec-trodeposition mechanism of chromium trivalent has not been fully elucidated,especially the intermediate process and con-trol steps of chromium ion reduction.Therefore,it is the key to solve a series of problems in the deposition process to study the plating solution system and electrodeposition mechanism of trivalent chromium in different plating solutions.Chromium electrodeposition process includes chromium electroplating and electrolysis.Based on the trivalent chromium electrodeposi-tion process,the electroplating and electrolysis were summarized and analyzed from two aspects,focusing on the mechanism of chromium electrodeposition,the composition and component application of chromium plating solution,and diaphragm chromium electrolysis.Finally,the future research direction of trivalent chromium electrodeposition was prospected,such as further improving the membrane electrolysis device and studying the nonlinear non-equilibrium behavior of chromium dur-ing deposition.
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.
Silicon manganese slag is an industrial by-product produced in the production of silicon manganese alloy.With huge annual discharge and low comprehensive utilization level,it has become an urgent problem for the green development of metallurgy industry.In order to realize high value utilization of silicon manganese slag,zeolite was prepared from silicon manganese slag by hydrothermal synthesis reaction of"pickling-alkali melting-aging-crystallization".X-ray diffractometer(XRD),scanning electron microscope(SEM),Fourier infrared spectrometer(FT-IR),surface area and aperture analyzer were used to characterize the crystal phase,morphology and functional groups of zeolite.The effects of alkalinity,tempera-ture and time on the phase composition and morphology of zeolite were investigated.The experimental results showed that the contents of MnO,Fe2O3 and CaO were reduced after acid leaching,and silicates required for zeolite synthesis were gen-erated in the alkali melting system.The zeolite with good purity and crystallinity was synthesized under the optimum condi-tions of 0.5 mol/L alkalinity,80℃temperature and 8 h.Compared with traditional industrial solid waste preparation of zeo-lite,the alkalinity required for crystallization in this experiment was lower,and silicon manganese slag was used as raw ma-terial to prepare zeolite,which provided a new idea for the high value utilization of silicon manganese slag.
The separation and extraction of low concentration boron from salt lake brine can not only improve the compre-hensive utilization rate of resources,but also solve the problem of boron impurity interference in the downstream products of salt lake.Graphene oxide/carbon nanotube(GO/CNTs)composite aerogel was synthesized by hydrothermal method.Polyhy-droxy 2-amino-1,3-propanediol was grafted onto the surface of the aerogel by epoxy ring-opening reaction to obtain amino alcohol modified graphene oxide/carbon nanotubes(GO/CNTs)aerogel gel boron adsorbent.The effects of pH,initial concen-tration,temperature and contact time on boron adsorption were studied by FT-IR,XPS and SEM.It was found that the adsor-bent was a porous structure with abundant polyol groups in the channel and on the surface.The results also showed that the maximum equilibrium adsorption capacity of boron was 43.42 mg/g at pH=10,Co=1 200 mg/L.The adsorption performance of boron was the best at 35℃and reached saturated adsorption equilibrium within 60 min.The adsorption process was ac-corded with quasi-second-order kinetic model.The adsorption mechanism was the chemical complexation between boron and polyhydroxyl groups.According to the research,the adsorbent showed good application value and potential in the separa-tion of boron in brine.
Phosphorite needs flotation treatment to be used in the wet phosphoric acid process.Phosphorite with low phos-phorus content is not suitable for phosphoric acid production and discarded,resulting in the accumulation of a large number of phosphorous tailings,which will not only cause environmental pollution,but also cause waste of resources if it is not ratio-nally used.Since there are still more elements such as calcium and magnesium in the phosphorus tailings,the phosphorus tailings can be used according to the enrichment of the elements.Therefore,the occurrence and distribution of main ele-ments such as calcium and magnesium in phosphorus tailings were analyzed by X-ray diffraction analyzer,inductively coupled plasma mass spectrometer,Raman spectrometer,scanning electron microscope,electron probe and X-ray photo-electron spectroscopy.The results showed that calcium was widely distributed in phosphorus tailings,and a large amount of calcium existed in the form of dolomite combined with magnesium,while a small amount of calcium existed in the form of fluorapatite and other calcium-containing compounds with fluorine and phosphorus.Through the complete analysis of phos-phorus tailings,the existence form and occurrence state of each element were obtained.It provided guidance for further utili-zation of calcium and magnesium in phosphorus tailings.
Fe2P is a common by-product during the generation of lithium iron phosphate(LiFePO4,LFP),and its effect on the electrochemical performance of LFP has not been thoroughly studied so far.The effect of adding different proportions of Fe2P into LFP by ball milling method on the electrochemical performance of LFP cathode materials was explored.The results showed that after doping Fe2P,the crystal structure of LFP material remained unchanged,the particle morphology was highly organized,and the distribution of major elements was uniform.Additionally,the ion and electron conductivity of LFP material were improved to varying degrees.Especially,when the Fe2P doping amount was 0.5%(mass fraction),the first dis-charge specific capacity reached 158.2 mA·h/g and 148.5 mA·h/g at 0.1C and 0.5C magnification,which were 8.90%and 7.2%higher than pure LFP,respectively.The difference in redox peak potential in CV curve(ΔE)was only 0.264 V,indicating that the introduction of Fe2P was beneficial for improving the polarization of LFP materials,and the high overlap of the first three CV curves indicated that the material had a high degree of reversibility.The charge transfer resistance(Rct)was only 41.56 Ω,which was 76.49%lower than pure LFP.The diffusion coefficient of lithium ions was 8.20×10-9 cm2/s,which was 89.4%higher than pure LFP.At the same time,the improvement on rate capability and cycling performance was significant.
