Using dolomite calcined powder as raw material,the Ca and Mg elements were separated by ammonium leaching method,and then high-purity nano-MgO was prepared by carbonization method,and the more suitable process conditions for carbonization reaction,heavy magnesium water pyrolysis,basic magnesium carbonate calcination and other processes were investigated and determined as follows:carbonization reaction process:carbonization endpoint pH value of 7.5,CO2 flow rate of 0.4 L/min,reaction temperature of 15℃,stirring rate of 400 r/min;Under these conditions,the conversion rate of MgO could reach 87.79%.Mg(HCO3)2 solution pyrolysis process:pyrolysis temperature of 95℃,pyrolysis time of 40 min;Under these conditions,the pyrolysis rate of Mg(HCO3)2 solution reached 94.46%,and the pyrolysis intermediate product was monoclinic 4MgCO3·Mg(OH)2·4H2O.4MgCO3·Mg(OH)2·4H2O calcination process:calcination temperature of 700℃,calcination time of 1 h.Under the above optimization conditions,the MgO content of the prepared MgO sample reached 99.11%,and the XRD and FE-SEM characterization of the sample showed that the prepared MgO sample was a cubic crystalline nano-MgO with a particle size of about 30 nm.
In order to solve the problems of mineral condensation and algae removal technology,such as asynchronously remove nitrogen and phosphorus,easy loss of minerals,a ldge amount of sediment,and short duration of removal effect.The adsorption and removal properties of NH4+-N,TP,Chl-a and TUB by 11 mineral materials were determined and screened.Five types of unburned green zeolite based composite materials(NGZC)were prepared based on green zeolite with the optimal NH4+-N adsorption effect.The NGZC surface structure was observed,the influences of the amount of foaming agent and cement,the material ratio of green zeolite and the other minerals on the water purification performance were discussed and the effects of factors such as amount of NGZC dosage,reaction temperature and time of water treatment on the removal of multiple pollutants from river sewage were also discussed.The results showed that under the set curing conditions,the optimal preparation conditions were as follows:10%-15%cement,0.25%-0.5%foaming agent,mass ratio of green zeolite and oyster shell,convex clay,active clay,hydrotalatite,red jade soil for 8∶2,4∶6,6∶4,4∶6,4∶6.The optimal water treatment conditions were as follows:adding 4 g NGZC in 200 mL polluted river water at 25℃,and the best treating time was 3 d.This study can provide low-cost composite water purification materials and new technologies for the pollution remediation of algal eutrophic water bodies,the resource utilization of non-metallic minerals,and water and soil conservation,etc.
Laterite-type weathered ilmenite has high mud content in the raw ore due to the more complete weathering degree,which makes the traditional process of sorting more difficult,and the TiO2 grade in the concentrate is more difficult to achieve the quality requirements of the industry standard under the premise of guaranteeing the recovery rate.In this paper,for the rough concentrate of lateritic weathered ilmenite with TiO2 grade of 43.92%,ultrasonic cavitation effect was used to desliming and removing impurities to achieve the purpose of further improving TiO2 grade.The relationship between ultrasonic frequency,stirring time,stirring speed,slurry concentration and the desliming rate and grade of ilmenite crude concentrate was investigated in a conditional test.The results showed that under the ultrasonic frequency of 30 kHz,stirring time of 30 min,stirring speed of 2 000 r/min,and slurry concentration of 30%,a titanium concentrate with a desliming rate of 7.88%,a TiO2 grade of 46.05%,and a recovery rate of 96.58%was obtained.The final product quality met the industry standard YS/T 351-2015"ilmenite concentrate"for grade V quality requirements,providing technical reference for improving the quality and reducing impurities of similar titanium coarse concentrates.
After mixing Na2S2O8 with BaS solution,it will uniformly react to generate crystal forming SO42-,which can then undergo homoge-neous precipitation reaction with Ba2+ to generate BaSO4.BaSO4 powders were prepared using them as raw materials,the crystal phase,morphology and particle size distribution of BaSO4 were characterized,and the factors affecting the particle size of BaSO4 powder were studied.The results showed that changing the addition method of Na2S2O8 from one complete addition to multiple equal additions,or increasing the reaction temperature,or decreasing the concentration of BaS solution,or reducing the amount of Na2S2O8 added,the average particle size of BaSO4 powder will significantly increase.After adding 0.3 mol Na2S2O8 into 0.5 mol/L BaS solution at reaction temperatures of 20℃and 100℃,the average particle sizes of the prepared powders were 0.727 μm and 0.873 μm,respectively.The results indicate that under appropriate reaction temperature,by adjusting the concentration of BaS solu-tion and the amount of Na2S2O8 added,the homogeneous precipitation method can directly prepare submicron BaSO4 powder.
In order to study the pyrolysis process of natural rock asphalt in north Sichuan,and investigate the effects of carbonization temperature and carbonization time on its pore structure and element composition during liquid phase carbonization,Guangyuan rock asphalt was used as raw material to prepare porous carbon materials by carbonation-activation method.The thermogravimetric analysis of raw materials showed that the main weight loss temperature range of rock asphalt was 400-600℃,the maximum weight loss rate present in 450℃,and the residual carbon rate was 56.35%at 1 000℃.Increasing carbonization temperature and extending carbonization time would promote the pyrolysis and polycondensation reaction of asphalt,its aromaticities and hydrophobicity were enhanced,while the polarity decreased,at the same time,its volatile components were continuously expelled and the polycyclic aromatic molecules tended to be arranged in a directional manner.The specific surface area increased during this process.ASUK4-2 had a maximum specific surface area,which was 365.14 m2/g.The nitrogen adsorption-desorption isotherms curve of each sample belonged to type II,and there was a hysteresis loop of type H3.The pore size distribution was mainly mesoporous,with a few large pores and micropore.This research provided a reference significance for investigating the carbonization process and material structure changes of natural rock asphalt under high temperature environment.
Modified palygorskite(Pal)was prepared with pal after acid-treatment and organic modification via one-step hydrothermal treatment,and its properties and viscosity were studied.The results showed that acidification could remove soluble impurities and dissociate Pal crystals,increased the specific surface area and pore size of Pal,but the viscosity of Pal was not correspondingly increased.The organic groups were grafted on the surface of Pal crystals by modification of cetylammonium bromide(CTAB)and the hydrophobicity of those carbon chains could stabilize Pal particles in the solution which increased the viscosity of the modified Pal effectively.After pickling,CTAB was introduced,which did not affect the structural properties of Pal,and greatly improved the viscosity of the modified Pal in aqueous solution.The viscosity of Pal could reach to 1 280 mPa·s when the concentration of HCl and CTAB were 1 mol/L and 10 g/L,respectively.Although the positive charge on Pal surface was increased after cationic adsorption of the modifier,it also dispersed Pal crystal and increased the Pal surface exposure.The hydrophobicity of CTAB carbon chain made Pal particles stable,further increased the absolute value of zeta potential of Pal,increased the repulsive force between Pal particles,and greatly increased the viscosity of modified Pal in water.The surface positive charge of Pal and the quantity of carbon chain were further increased with the modifier concentration,resulting in the decrease of the negative charge and the absolute value of zeta potential of the modified Pal,its viscosity was reduced.
In this paper,collaborative flotation process of PMS/O3 was used to study the whitening and purification of phosphogypsum.The effects of single factors such as PMS concentration,solid-liquid ratio and reaction time on the whiteness of phosphogypsum were investigated,the optimal process conditions for stirring leaching test were obtained by designing orthogonal experiments based on single factor effect results.On this basis,purification and whitening of phosphogypsum were studied through reverse flotation experiments.The results showed that the whiteness of phosphogypsum increased from 27.8%to 68.3%,when the concentration of PMS was 5%and stirring with ozone for 2.5 h.When the concentration of PMS was 5%,a PMS/O3 synergistic flotation process was adoped,the whiteness of phosphogypsum increased from 27.8%to 77.2%,the impurity P2O5 decreased from 1.33%to 0.24%,and F was not detected,thereby expanding its application in building materials and other fields.
The fluorinated sludge produced in semiconductor industry is increasing rapidly,it is difficult to achieve the utilization of fluorine resource via traditional methods because of complex composition and small particle size.This study systematically investigated the mineral composition,particle size and micro-morphology of fluorinated sludge produced by a semiconductor company.The results showed that the flocculant added in the previous wastewater treatment process agglomerated calcium fluoride and impurities into large particles,which seriously affected flotation effect purification.The acidic dissociation of fluorinated sludge could be effectively achieved by treating the sludge using hydrochloric acid as the depolymerization reagent.The concentrate of calcium fluoride with CaF2 grade of 84.41%and recovery of 75.72%was obtained by one stage of roughing,three stages of selecting and three stages of sweeping,using sodium oleate as collector and acidified waterglass as inhibitor.This paper provided theoretical guidance and scientific basis for the separation,purification and resource utilization of fluorinated sludge produced in semiconductor industry.
Using aluminum factory sludge,kaolin tailings,and nickel slag as the main raw materials,the effects of different raw material ratios,firing temperature,and holding time on the content and structure of synthesized mullite were studied.The products were characterized by XRD and SEM.The results showed that sample of 3#(64%aluminum factory sludge,25%kaolin tailings,and 11%nickel slag)could synthesize a total content of mullite up to 80.5%,with a content of 3Al2O3·SiO2 up to 63.7%.Taking into account production cost factors,at a firing temperature of 1 400℃and insulation for 4 h,the stable mullite content synthesized by sample 3#is the highest,forming a strong network like structure.
In order to study the improvement effect of fiber on cracks in expansive soil,dry and wet cycle tests were carried out on plain expan-sive soil and reinforced expansive soil.The fracture photos were vectorized by vector mapping technology to explore the fracture development law of expansive soil and the influence of different lengths(3 mm,6 mm,9 mm)and dosages(0.1%,0.2%,0.3%,0.4%,0.5%)of fibers on the fracture area rate of expansive soil.The results showed that the fracture development of expansive soil was divided into rapid development stage,slow development stage and healing stage.When the tensile stress caused by the moisture content gradient was greater than the tensile stress of the soil sample itself,cracks would occur,and with the increase of the number of dry and wet cycles,the fracture area rate would continue to increase,and the fracture would stop developing when the tensile stress was greater than the tensile stress.When the fiber length was fixed,the fiber content with the best effect on the improvement of the fracture of expansive soil should be 0.3%;The fracture area rates of expansive soil with fiber length of 3 mm,6 mm and 9 mm and 0.3%content were reduced by 31.98%,48.12%and 62.45%,respectively.That is,when the fiber content was fixed,the longer the fiber length,the smaller the fracture area rate of the soil.
A lead-zinc smelting waste was utilized to prepare a non fired brick with high compressive strength and good heavy metal solidification effect using microbial cement technology.The influence of particle size and addition amount of lead-zinc smelting slag on the dry density,compressive strength,and phase composition were studied,meanwhile,we explored the solidification mechanism and existing forms of heavy metals.The results showed that increasing the fineness and addition amount of lead-zinc smelting slag appropriately could improve the dry density and compressive strength of unburned brick products.When adding 50%(mass ratio)lead-zinc smelting slag and the particle size of-0.074 mm accounting for 60.25%,the unburned brick exhibited the best performance for dry density of 2 258.96 kg/m3 and compressive strength of 35.48 MPa,and the leaching concentration of Pb2+ and Zn2+ in the sample was lower than the standard requirements.Carbonate precipitates difficult to dissolve in water was formed by combination of CO32-,which was generated by the urea decomposition of Bacillus subtilis with heavy metal ions in lead-zinc smelting waste,thus achieving the solidification of heavy metal ions.XRD and SEM analysis showed that the products had a dense microstructure and high strength for the cooperation of the hydrated calcium silicate and xonotlite gel products generated in the hydration process and Bacillus pasteureus metabolic product calcium carbonate.
To solve the problem of efficient dewatering of flotation tailings rich in clay minerals,we use ultrasound to treat polyacrylamide(PAM)and explore the effects of ultrasound modified and unmodified PAM on the flocculation settlement and filtration efficiency of kaolin.The results showthat the lowest turbidities of the supernatant for probe-and tank-type ultrasound systems are 49.2 NTU(200 W input power and 10 s treatment time)and 41.3 NTU(600 W input power and 15 s treatment),respectively.Both probe-and tank-type ultrasonic treatment can significantly reduce the resistance during the formation of kaolin filter cake,thereby greatly shortening the filtration time.
Regenerated micro powder is a byproduct of the reuse process of construction waste,its chemical composition and phase composition are basically consistent with cement,so it has the potential to replace cement.This article uses stone powder as a control group to study the effect of regenerated micro-powder on cement properties,and explains the mechanism of action that affects cement hydration from a microscopic perspective.The results show that regenerated micro powder has the potential to replace cement as a mixture,with a volcanic ash activity of 58.9%,belonging to the inert mixture.Regenerated micro powder will reduce the standard consistency water requirement of the prepared cement,but the degree of reduction is smaller than that of stone powder.Both regenerated micro powder and stone powder can shorten the setting time of cement.At the same dosage,the effect of regenerated micro powder on shortening the initial setting time of cement is more obvious,while stone powder has a more significant effect on shortening the final setting time of cement,both meet the OPC setting time requirements of GB 175-2007.The addition of recycled micro powder and stone powder will reduce the compressive strength of cement.The amount of recycled micro powder should not exceed 10%,and when the amount of stone powder should not exceed 15%,both meet the P·O 42.5 strength requirements of GB 175-2007.The reduction effect of regenerated micro powder on hydration heat release is more significant,and it has the potential to be used in large volume concrete.In summary,compared to stone powder,regenerated micro powder has a more significant effect on reducing the performance of cement.However,when the dosage is not more than 10%,the prepared cement can still meet the requirements of relevant specifications,providing a broader way for the resource utilization of regenerated micro powder.
In order to achieve the utilization of industrial solid waste and reduce cement usage,lithium slag is used as the main admixture,and self igniting coal gangue and steel slag are partially substituted for cement to prepare composite cementitious materials.The effects of admixture ratio and cement replacement rate on the mechanical properties and microstructure of cement mortar are studied.The results show that when the ratio of lithium slag,spontaneous combustion coal gangue,and steel slag in the composite admixture is 4∶1∶1,the compressive strength at 28 d reaches 51.98 MPa,and the later compressive strength of replacing 30%cement does not decrease significantly compared to the 25%dosage.The microscopic results show that the admixtures do not change the type of hydration products,mainly calcium silicate hydrate,calcium hydroxide and vanadite;The active components SiO2 and Al2O3 in the composite admixture undergo a secondary hydration reaction with Ca(OH)2,generating more hydrated calcium silicate and calcium vanadate,which synergistically hydrate and promote the improvement of strength.
To improve the purification performance of TiO2 photocatalytic materials for heavy metal Cr(Ⅵ)in waste water.La-TiO2/kaolinite composites photocatalytic materials were prepared by sol-gel method with kaolin,lanthanum nitrate and tetrabutyl titanate as raw materials.The samples were characterized by XRD,SEM/EDS,and UV-Vis.The performance of adsorption and visible light photocatalytic reduction removal for Cr(Ⅵ)on samples prepared by different modification methods were studied.The results showed that La doping could refine TiO2 grains,stabilized phase structure of anatase TiO2,and expanded its absorption spectrum threshold,thereby enhancing its photocatalytic reduction activity of Cr(Ⅵ).Due to the composite of kaolin,the dispersion of TiO2 samples was improved and it was endowed with a large specific surface area,its adsorption ability for Cr(Ⅵ)was enhanced.The adsorption equilibrium process of TiO2 for Cr(Ⅵ)conformed to the Langmuir model.The coupling effect of doping and composite modification improved the adsorption and visible light catalytic reduction removal efficiency of Cr(Ⅵ)in composite material samples.The adsorption-photocatalytic purification efficiency of La-TiO2/kaolinite for Cr(Ⅵ)under visible light irradiation for 6 hours reached the highest of 96.5%.The apparent first-order kinetic constant of its photocatalytic reduction reaction was 2.6 times that of pure TiO2.
In order to investigate the impurity eliminations method of phosphogypsum in Hubei Province,improve the purity and whiteness,the automatic mineral analysis system(AMICS)was applied to systematically investigate the process mineralogy,including the mineral composition and characteristics,the elemental distribution,the particle size distribution,the embedded characteristics and dissociation of important minerals.The process mineralogy showed that the main minerals of the phosphogypsum sample were gypsum with a content of 80.46%,followed by quartz and feldspar,phosphate rock,and a small amount of muscovite,plagioclase and barite.The metallic minerals mainly included pyrite,limonite and rutile with low content.The results showed that wet ball milling significantly improved the whiteness of the flotation concentrate,but with the increase of grinding time,the contents of silicon,organic matter and soluble P2O5 were reduced.The phosphogysum concentrate indexes were the best when the grinding time was 8 min,its yield was 73.56%,whiteness was 73.89%,SiO2 content was 1.81%,soluble P2O5 content was 0.069%,soluble F-content was 0.032%,and organic matter content was 0.012%.
To study the effect of EPS particles on the performance of fly ash-based alkali-activated lightweight materials,the changes in physical properties,compressive strength,and frost resistance of the lightweight fly ash-based alkali-activated aeolian sand composite material were investigated by adding EPS particles alone.The results show that the larger the amount of EPS particles added,the faster the decrease rate of dry apparent density and compressive strength of the specimen;When the EPS particle content is 10%-70%,the dry apparent density of the material is between 792-1 864 kg/m3;An increase in the amount of EPS particles will cause the slurry bonding layer between lightweight aggregates in the matrix to become thinner,which is detrimental to the material strength;After 100 freeze-thaw cycles,the maximum mass loss rate and relative dynamic modulus of the composite material at each dosage are less than 0.4%and more than 93%,respectively,indicating that the fly ash-based alkali-activated aeolian sand lightweight composite material has good frost resistance performance.Based on experimental data,a freeze-thaw degradation model for fly ash-based alkali-activated lightweight composite materials with different EPS particle dosages is established,which has specific reference significance for predicting the freeze-thaw damage process of materials.
Sound-absorbing ceramsite is widely used as producing sound barriers and sound-absorbing panels in fields such as construction and transportation,the main raw materials of existing ceramsite are exhaustible resources such as clay and shale.For trying to solve the problem of large existing stock and hard utilization of red mud,coal gangue and waste rock powder in China,a green and environmentally friendly high-performance sound-absorbing ceramsite is prepared by using Bayer red mud,coal gangue,and waste mechanism sand powder through disc forming and sintering process.By observing the macroscopic morphology and testing the physical rationality,the optimal sintering temperature of ceramsite can be explored,and the radioactivity of ceramsite can be measured,the optimal sound absorption coefficient of ceramsite concrete standard specimens is determined using the standing wave tube method and flow resistance test.The results show that the ceramsite sintered at 1 120℃have the best performance,with a cylinder compressive strength of 7.0 MPa,a bulk density of 947 kg/m3,an internal irradiation index of 0.6,and an external irradiation index of 1.0;When the water cement ratio is 0.2 and the flow resistance is between 2 535-3 429 Pa·s/m2,the average sound absorption coefficient of the standard specimen of ceramsite concrete is the best,which is 0.50.The physical properties of sound-absorbing and noise reducing ceramic particles meet the re-quirements of GB/T 17431.1-2010"Light Aggregates and Test Methods-Part 1:Light Aggregates"for high-strength artificial light aggregates,and the radioactivity meets the requirements of GB 6566-2010"Limits of Radionuclides in Building Materials"for building main materials.
To achieve the harmless utilization of urban construction waste and fly ash,a low-cost,high-performance cementitious filling material for mine goaf backfilling was developed.A four-factor,three-level orthogonal experimental design was used to determine the optimal parameters for the filling material and elucidate its strength mechanism.The results showed that slurry concentration,sand-cement ratio,and Ca(OH)2 content were positively correlated with the compressive strength and yield stress of the filling material,while consistency,slump,and setting time were negatively correlated.Among the factors,slurry concentration had the greatest impact.The optimal parameters were as follows:sand-cement ratio of 1∶3,fly ash to cement mass ratio of 8∶2,Ca(OH)2 content of 10%,and slurry concentration of 70%.The hardening mechanism involved the activation of fly ash by Ca(OH)2,leading to the formation of C-S-H gel,calcium aluminate,and intermediate hydration products C2S and C3S,resulting in a 28 d total hydration product loss of 5.39%.The construction waste particles in the filling material were covered by hydration products,resulting in a denser structure with reduced porosity.
Taking the pretreated copper tailings as the research object,the effects of the treated copper tailings on the calcination process of cement clinker properties and the properties of clinker were studied when the siliceous raw materials were replaced by treated copper tailings with high content or full content(5%,10%,15%and 18.22%).The results show that when the treated copper tailings are high or even completely replace siliceous raw materials,the burnability of raw meal becomes better,and the difficulty of C3S generation is reduced.Before and after the incorporation of copper tailings,the crystal structure of C3S in the clinker did not change,and the crystal form was M3 type.The standard consistency and water consumption,setting time and stability of cement clinker calcined at 1 450℃all meet the specifications in GB/T 21372-2008"Portland cement clinker",and its mechanical properties are significantly improved compared with those without copper tailings.
