The SAPO-34 molecular sieve，owing to its CHA topology，moderate acidity，excellent anti-coking properties，and superior hydrothermal stability，has been widely employed in various catalytic reactions.The synthesis methods of SAPO-34 molecular sieves were introduced briefly.Novel synthesis strategies such as nano-sizing and hierarchical pore structure regulation were introduced in detail.The principle and characteristics of the synthesis methods of nano SAPO-34 molecular sieve and hierarchical porous SAPO-34 molecular sieve were summarized.Subsequently，the factors influencing the synthesis of SAPO-34 molecular sieves were discussed，including precursor composition and ratio，structure-directing agents，seeds and crystallization conditions，all of which collectively affect crystallinity，crystal morphology，and particle size.Furthermore，the practical applications of SAPO-34 molecular sieves in catalytic reactions such as methanol-to-olefins（MTO） and selective catalytic reduction of nitrogen oxides with ammonia（NH₃-SCR） were reviewed.Finally，prospects for achieving greener and more efficient synthesis of SAPO-34 molecular sieves were outlined.

The intensifying global greenhouse effect has drawn significant attention to the application of mineral carbonation technology in the cement industry.In view of the high energy consumption associated with Portland cement production，the utilization of processed calcium-based industrial solid wastes as substitutes has emerged as a more sustainable solution.In this paper，typical calcium-based industrial solid wastes such as fly ash，steel slag，calcium carbide slag，by-product gypsum and cement-based construction waste were taken as representatives.The CO₂ sequestration mechanism，adsorption potential，application prospect and added value of calcium-based industrial solid wastes were reviewed according to the source，composition and physicochemical properties.Furthermore，it provided a detailed discussion on the optimization of carbonation reaction conditions，the utilization of carbonated byproducts，and the potential impact on concrete workability and long-term performance activity.Future research should focus on continuously optimizing the kinetic parameters of carbonation reactions and developing efficient synergistic activation processes to enhance the substitution ratio of industrial solid wastes in construction materials.With the aim of achieving large-scale resource utilization of industrial solid wastes and facilitating the low-carbon transition of the cement industry，these efforts would provide technical support and economic guarantees for achieving global carbon neutrality.

Due to the widespread application of NCA-type lithium-ion power batteries in the new energy field and the high value of the elements they contained，in order to enhance the advancement of recycling technologies for used batteries，the "roasting-water leaching" technology was proposed to replace the acid leaching technology in the hydrometallurgical recycling process.The phase changes during the recycling process and the main factors affecting the recovery rates of Li，Co，and Ni elements were studied through TG-DSC，XRD，XPS，SEM-EDS，thermodynamic analysis，and ICP-OES.The research results showed that a chemical transformation occured during the mixed roasting process，generating new phases，accompanied by obvious weight loss and endothermic phenomena.When the mass ratio of LiNi_0.8Co_0.15Al_0.05O₂（NCA） to KHSO₄ reduced from 1:0.14 to 1:1.84，the phase change rules were as follows Li：LiNi_0.8Co_0.15Al_0.05O₂→Li_0.21Co_0.79O and KLiSO₄；Ni：LiNi_0.8Co_0.15Al_0.05O₂→NiO and K₂Ni₂（SO₄）₃；Co：LiNi_0.8Co_0.15Al_0.05O₂→Li_0.21Co_0.79O and K₂Co₂（SO₄）₃.The valence states of Ni and Co elements evolved as follows Ni：+2，+3→+2；Co：+3→+2，+3.Under the conditions of a mass ratio of NCA to KHSO₄ of 1:1.84，roasting at 600 ℃ for 0.5 h，water leaching at 50 ℃ for 0.5 h，a stirring rate of 120 r/min，and a liquid-to-solid ratio of 25:1 （mL/g），the leaching rates of Li，Co，and Ni were 95.10%，52.68%，and 10.42%，respectively.Compared to traditional hydrometallurgical processes，this technology avoided the use of strong acids and enhanced the overall recovery rate of valuable metals through the selective extraction of lithium elements，contributing to the economic efficiency of recycling spent lithium-ion power batteries.

Among various strategies，lithium-aluminum layered double hydroxides（Li/Al-LDHs，hereinafter referred to as LDHs） are regarded as one of the most promising adsorbents for efficient lithium extraction from salt lake brines.However，the application of LDHs is hindered by their susceptibility to excessive Li⁺ desorption during the desorption process，which leads to structural collapse，inactivation，and an actual adsorption capacity that is significantly lower than the theoretical value.To address these limitations，a strategy was proposed to enhance the stability，selectivity，and adsorption capacity of LDHs through a one-pot synthesis method incorporating Ni（NO₃）₂ doping modification.By partially replacing Al sites in the LDHs framework with Ni，the affinity for Li⁺ was improved while reducing the affinity for competing metal ions.The effect of varying aging times on the performance of Ni-LDHs-NO₃ was also investigated.The results revealed that Ni-LDHs-NO₃ synthesized with an aging time of 10 min achieved an adsorption capacity of 9.18 mg/g in a 300 mg/L LiCl solution，significantly surpassing traditional LDHs（4.51 mg/g）.The adsorption rate was substantially improved，reaching equilibrium within 100 min.Notably，the separation factors for Li⁺/Na⁺，Li⁺/Mg²⁺，and Li⁺/K⁺ were 339.59，566.15，and 108.52，respectively，highlighting that Ni doping effectively modified the material′s ion affinity and enhanced its adsorption kinetics.Moreover，the adsorbent retained 89.27% of its initial capacity after 10 adsorption-desorption cycles，demonstrating remarkable cyclic stability.These findings underscored the potential of Ni-LDHs-NO₃ as a high-performance adsorbent for Li⁺ extraction from brines.

In order to develop potassium and lithium resources in the deep brine from Mahai region，through the statistics and comprehensively comparison of hydrochemical characteristics of the deep brine and subsurface brine from Mahai region firstly，it was determined that the deep brine of this experiment was in the transition stage from subsurface brine to deep brine.The type of experimental brine was still magnesium sulfate subtype，and its hydrochemical characteristic parameter m（KCl）/m（MgCl₂） was so high to 0.519 that it was nearer to the composition point of phase KCl，with prolonged precipitation rate of the sylvinite section.Then，through the indoor evaporation experiment at 15~25 ℃，chemical compositions of stage liquid and solid phase，and XRD patterns analysis，laws including the evaporation route of Mahai deep brine，hydrochemical characteristics，elemental behaviors were determined.The evaporation was divided into three stages：halite，sylvinite and carnallite，potassium was deposited in two phases，KCl and Car，with phase KCl accounting for 61% of total potassium precipitation，and the carnallite section was accompanied by deposition of phase epsomite and phase bischofite.Trace elements such as Li，B，and Br were always concentrated in the form of ions，and the ion concentration had reached more than 0.2 g/L in the bittern.Finally，there was a good match between experimental results and theoretical evaporation calculations，theoretical calculations of the metastable phase diagram 25 ℃ Na⁺，K⁺，Mg²⁺//Cl^-，SO₄^2--H₂O could be used to guide the actual Mahai deep brine evaporation better.The results provided theoretical support for the exploitation and comprehensive utilization of Mahai deep brine.

The preparation of high-purity pseudo boehmite using aluminum isooctanol as raw material can solve the problems of pipeline blockage and high energy consumption in alcohol water separation caused by the hydrolysis of aluminum isopropoxide in industry.The influence of different hydrolysis conditions on the solubility index and gelation time of pseudo boehmite was studied by changing the hydrolysis temperature，hydrolysis time，aging temperature，and aging time during the preparation of high-purity pseudo boehmite by hydrolysis of isooctanol aluminum and combining XRD analysis of the crystal phase of the product.The results showed that changes in hydrolysis temperature，hydrolysis time，aging temperature，and aging time all affected the solubility of pseudo boehmite，with hydrolysis temperature having the most significant effect.The solubility index of pseudo boehmite obtained by hydrolysis at 95 ℃ could reach over 99.9%，and the shortest gelation time was 8 seconds.After hydrolysis at 95 ℃，different aging times and temperatures had no significant effect on the solubility index of the product，which could reach over 99.9%.To further improve the solubility of the product，the hydrolyzed product was treated in a pure water system at 110 ℃，and the gelation time was shortened to about 5 seconds，exhibiting various technical parameters comparable to commercial high-purity pseudo boehmite（SB powder）.This study provided a research foundation for the large-scale production of high-purity pseudo boehmite prepared by hydrolysis of isooctanol aluminum.

This paper was aimed to address the problem of excess powder alkali and carbon dioxide in the calcination section of the ammonia-soda process and to explore the reaction and crystallization mechanism of sodium carbonate and carbon dioxide.Therefore，sodium carbonate and carbon dioxide were taken as the research objects to investigate the effect of the concentration of Na₂CO₃ solution，the flow rate of CO₂，and the reaction crystallization temperature on the reaction and crystallization process.Raman spectrometer was used to monitor the changes in the intensity of characteristic peaks of Na₂CO₃ and NaHCO₃ with reaction and crystallization time.Through standard curve regression and phase diagram analysis，the change path of the reaction system point，reaction rate，nucleation rate，and crystallization rate were determined.The reaction and crystallization of sodium carbonate and carbon dioxide could be divided into three stages：the reaction stage of sodium carbonate and carbon dioxide，the nucleation and growth stage of sodium bicarbonate.The maximum reaction rate of Na₂CO₃ and CO₂ was 0.450 mol/（kg·min），and the crystallization rate（including nucleation and growth process） of NaHCO₃ was 0.083 mol/（kg·min）.The reaction rate was the fastest and the crystallization rate was the lowest in the three stages of the reaction and crystallization of sodium bicarbonate，indicating that the crystallization of sodium bicarbonate was the rate-controlling step of this process.With the increase of CO₂ flow rate and temperature，the reaction rate，nucleation rate，and crystallization rate were all increased.With the increase of alkali solution concentration，the reaction rate of sodium carbonate and carbon dioxide and the crystallization rate of sodium bicarbonate were both decreased，while the nucleation rate of sodium bicarbonate increased，and the change path of the system point changed significantly.Eventually，they entered the single solid phase crystallization zone of sodium bicarbonate，the eutectic zone of sodium bicarbonate and sesquicarbonate，and the eutectic zone of sodium bicarbonate，sesquicarbonate and monohydrate sodium carbonate，respectively.

Magnesium borate is an important boron-containing raw material in the production of alkali-free glass fiber and ceramics.To address issues such as slow reaction rates，low yields，and high costs in the laboratory synthesis of the hydrated magnesium borate（e.g，macallisterite） for glass applications，a study was conducted on the crystallization process and kinetics of macallisterite in the concentrated salt solutions of MgCl₂-xNa₂O·yB₂O₃-H₂O.Firstly，based on MgCl₂·6H₂O，NaOH and H₃BO₃ as raw materials，the response surface methodology（RSM） was used to design and optimize the crystallization process conditions of macallisterite，and a crystallization yield prediction model was established.Secondly，based on the theory of crystal growth diffusion，the crystallization mechanism and kinetics of macallisterite were studied，and the crystallization rate equation was obtained.Finally，based on the comprehensive utilization strategy of boron and magnesium resources in salt lakes，the old brine saturated with magnesium chloride was used as raw matrerials to synthesize the macallisterite.The results showed that the predicted boron crystallization yield was 80.56% in B₂O₃ according to the RSM model，and the experimental value was 81.58% with a relative error of 1.25%.It indicated that the model was reliable and the crystallization yield was improved.The growth mechanism of the macallisterite was the multi-nucleus controlled crystal surface growth model of MA-2，and the crystallization rate was significantly increased.The crystallization yield of the macallisterite synthesized from the old brine was more than 74%，which was lower than that of the optimization experiment.The main reason was due to the decrease in boron concentration and the different mechanisms by which coexisting SO₄^2- ions affect the multi boron species in the solution.The above research not only provided technical support for the industrial production of hydrated magnesium borate for glass，but also provided new ideas for the comprehensive utilization of boron and magnesium resources in salt lake brine.

To investigate the mechanism of preparing dense fine-grained alumina ceramics using different sintering methods，Al₂O₃ ceramics were prepared using conventional high-temperature and atmospheric pressure sintering，high-pressure forming and atmospheric pressure sintering，and high-temperature and high-pressure sintering methods with 0.20 μm Al₂O₃ as the raw materials.The crystal structure，microstructure，and properties of the obtained Al₂O₃ ceramics were analyzed and characterized by X-ray diffraction，scanning electron microscopy，density，and Vickers hardness tests.The sintering mechanisms of high-pressure forming，atmospheric pressure sintering，and high-temperature high-pressure sintering were also explored.The results showed that dense Al₂O₃ ceramics could be obtained by all three sintering methods，and the relative densities of the samples were 96.64%，97.12% and 97.87%，respectively.Due to forming under a pressure of 5 GPa，the relative density of Al₂O₃ ceramic green body reached 60.02%.High pressure could make Al₂O₃ particles move closer quickly，accelerate plastic slip，eliminate small pores between grains，strengthen diffusion，and promote densification.Al₂O₃ ceramic with a grain size of only 0.22 μm was obtained after sintering at a lower temperature（1 000 ℃），which was slightly larger than the grain size of the raw Al₂O₃ powder，and the grain size was uniform.In high temperature and high pressure sintering，applied pressure could increase the driving force of sintering，and dense samples could be obtained at low temperatures for a short time.Since the grain size of the samples formed at high pressure and sintered at normal pressure was the smallest，the samples showed the largest Vickers hardness，which was 1 835.

In order to prepare polyaluminum chloride（PAC） with high effective content and stable performance，and effectively shorten the preparation time，a new gel method was used to prepare PAC.The preparation conditions of polyaluminium chloride by the new gel method were optimized as follows：aluminum hydroxide was reacted with slightly excessive sodium hydroxide under slightly boiling conditions to obtain a clear sodium metaaluminate solution.Hydrochloric acid was dropped into sodium metaaluminate solution to neutralize excess alkali.Then，under the conditions of heating and stirring，a quantitative amount of hydrochloric acid was added to the solution for reaction to obtain PAC products with a certain basicity.The results showed that when n（NaOH）/n［Al（OH）₃］ was 1.50，sodium meta-aluminate solution could be prepared in only 15 minutes.When the concentration of hydrochloric acid solution was 6.19 mol/L，the dropping speed was 15.00 mL/min，the heating temperature was 80 ℃，and the heating time was 0.5~1.0 h，the effective content of Alb in polyaluminum chloride was more than 80%.The prepared polyaluminum chloride was used for coagulation treatment of algae containing water samples.The results showed that when the dosage of n（OH^-）/n（Al³⁺）=2.0 homemade polyaluminum chloride was 6.6 mg/L，the turbidity removal rate of algae containing water samples with initial turbidity of 10~40 NTU was more than 90%，and the residual aluminum concentration was less than 0.20 mg/L.The new gel method could effectively shorten the preparation time，and the product had high effective content and good coagulation effect.

To investigate the reasons for degradation of separation performance of lithium extraction nanofiltration membranes in salt lakes，two-stage nanofiltration membranes retired from lithium extraction in Qinghai Yiliping Salt Lake were autopsied and analyzed by SEM，FT-IR，ICP，XRD，XPS to understand the morphologies and compositions of the membrane fouling layer.The results showed that both membranes of stage one and stage two were primarily suffered from organic and microbial pollution，with a mass fraction of 77% and 69% respectively.The organic pollution from stage one to stage two was gradually weakened，while the inorganic pollution was aggravated.The organic foulants were mainly lipids，proteins，nucleic acids，and polysaccharides，which originated from extracellular polymers（EPS） secreted by microorganisms and microbial metabolites.Mg，Ca，Al，Fe，Si，K，Na were the predominant inorganic elements，which were clay minerals deposition from salt lake sediments such as illite，chlorite，quartz，and albite.In addition，the retired membrane were subjected to chlorination during service.The accumulation of the above pollutants and chlorination were principal factors causing performance deterioration of the retired nanofiltration membranes.This research provided a basis for the efficient operation optimization and effective control of membrane fouling in future application.

The salinity of produced water from the Tarim oil and gas field in Xinjiang ranged from 10% to 20% and the wastewater contained the antifreeze methanol.To realize the resource utilization of freshwater and salt，it is essential to establish a sustainable and economic method for the degradation of organics.Due to the excellent salinity tolerance，biological contact oxidation reactor（BCOR） technology has been utilized to treat methanol-containing gas produced water（3.9% salinity）.However，the treatment efficiency under higher salinity conditions is still unclear.In this study，the synthetic methanol wastewater with 20% salinity was used as target wastewater.R1 and R2 were conducted to evaluate the treatment efficiency using direct start-up strategy and gradient salinity-elevation acclimation strategy，respectively.The results showed that the TOC removal efficiency of R1 was varied at 37.5%~77.6% with the influent TOC of 125 mg/L，reflecting its poor performance.The TOC removal efficiency of R2 was remained stable at 85.7%~93.6% with the influent TOC of 500 mg/L under salinities of 11%~13%，however，it was decreased to 61.6%~81.8% accompanied by significant methanol volatilization under salinities of over 15%，with the floatation and loss of sludge.Bacterial community analysis revealed that genera Methylophaga and Halomonas predominated at 13% salinity，while the abundance of genus Methylophaga decreased significantly with salinity exceeding 15%.Overall，the gradient salinity-elevation acclimation strategy significantly enhanced the performance of BCOR in treatment of ultra-high salinity wastewater.However，the effect of this strategy was limited in treatment of extremely high salinity wastewater（17%~20%）.This study provided reference for the biological treatment of ultra-hypersaline methanol-containing wastewater.

Power plant desulfurization wastewater is characterized by high salinity，high hardness，and complex composition.Due to the unclear laws of salt precipitation and basic physical properties during wastewater evaporation and concentration，it is difficult to achieve precise control of the evaporation and volume reduction treatment process，resulting in severe equipment scaling and low resource utilization.Therefore，based on the thermodynamic phase equilibrium laws of multi-component water-salt systems，the atmospheric evaporation and salt precipitation laws and crystal phase transformation behaviors of two typical types of desulfurization wastewater（chloride and sulfate types） were investigated.The changes in boiling point，concentration ratio，and ion composition of the wastewater under different evaporation rates were explored.The feasibility of guiding the evaporation and salt precipitation process design with thermodynamic phase diagrams was verified through experiments.The order of salt precipitation during evaporation for both types of wastewater was amorphous organic impurities，gypsum（CaSO₄·2H₂O），and sodium chloride.To ensure the separate precipitation of gypsum，the boiling points of the concentrated chloride and sulfate wastewater should be controlled at 106 ℃ and 108 ℃ respectively，with corresponding vaporization rates of over 85%.Additionally，it was found that calcium sulfate precipitated as gypsum（CaSO₄·2H₂O） in the initial stage of evaporation.In a high-temperature hydrothermal environment（>100 ℃），it began to dehydrate and transform into CaSO₄ within 240 minutes，with the transformation being completed in 360 minutes.It clarified the application conditions for the gypsum crystallization anti-scaling technology.The study provided key process parameters for the evaporation and volume reduction treatment of desulfurization wastewater，which had significant practical value for improving the water-saving and energy-saving capabilities of power plants.

Poor cycling stability is the main bottleneck restricting the development and application of calcium-based CO₂ adsorbent.The precursors were prepared from stone powder and steel slag，and the optimum conditions for preparing adsorbent were determined by response surface method.The influence and mechanism of steel slag on the cyclic stability of the adsorbent were studied by calcium cycle testing and SEM，XRD，BET detection.The results showed that the optimum conditions for preparation of the adsorbent were calcination temperature of 860 ℃，calcination time of 95 min，in an air atmosphere，mass ratio of stone powder，steel slag and cement 90:7:3，and at this time the effective decomposition value of the adsorbent was 94.06%.After 35 calcium cycles（GX₃₅），the CO₂ adsorption capacity and carbonation conversion rate of the adsorbent with steel slag were 0.426 1 g/g and 78.60%，respectively，which were better than the CO₂ capture performance of the adsorbent without steel slag after 20 calcium cycles（SX₂₀）.GX₃₅ contained a relatively large number of pores with diameters ranging from 1 nm to 3 nm and it had a loose sponge-like structure overall，while SX₂₀ contained few pores with diameters below 5 nm and it had a tight structure.The adsorbent with steel slag showed a smaller change in crystal growth and pore structure during the calcium cycle compared to the adsorbent without steel slag.Steel slag could play the role of accelerate decomposition，block separation，disperse limiting，skeleton support and nucleation，inhibited crystal aggregation and particle agglomeration，and reduced pore structure collapse and plugging amplitude，and enhanced the anti-sintering ability and cycle stability of the adsorbent.

To meet the demand for rapid detection of heavy metal ions in water，a novel electrochemical sensing platform based on phosphorus-doped cobalt phosphide modified phosphorus and nitrogen co-doped porous carbon tubes（CoP@P-N-C-550） was developed through a hydrothermal-carbonization-phosphidation coupled strategy.The electronic structure of the material was innovatively regulated by heteroatom doping and metal phosphide synergistic effect，and combined with the mass transfer advantage of the porous carbon tube morphology，the electron transfer efficiency at the electrode interface was significantly improved.The experimental results showed that in single-ion detection，the sensitivity for Cd²⁺ was 15.226 4 μA/（μmol/L） in the range of 0.05~6.00 μmol/L（LOD=5.36 nmol/L），and for Pb²⁺，it was 26.773 6 μA/（μmol/L） in the range of 0.50~6.00 μmol/L（LOD=3.13 nmol/L）.In simultaneous detection of two ions，the sensitivity for Pb²⁺ was increased to 37.008 8 μA/（μmol/L） and LOD was decreased to 2.20 nmol/L，effectively avoiding ion interference.The sensor exhibited excellent repeatability（RSD<2.4% for 10 preparations in detecting Cd²⁺ and Pb²⁺），and achieved high-precision recovery of Cd²⁺（91.00%~104.00%） and Pb²⁺（87.00%~104.33%） in real water samples（mineral and tap water），overcoming the traditional electrode's matrix interference bottleneck.This work provided a new strategy of interface engineering optimization for simultaneous detection of multiple metal ions and holds important application value in environmental monitoring.

Nitrogen-rich carbon nitride（C₃N₅） was loaded on the surface of montmorillonite MK30 to prepare C₃N₅/MK30 photocatalyst in situ.The crystal form，functional groups，elemental composition，spectral response，photoelectron-hole recombination and charge transfer resistance of the photocatalyst were characterized by X-ray diffraction（XRD），fourier transform infrared spectroscopy（FT-IR），X-ray photoelectron spectroscopy（XPS），UV-visible diffuse reflectance spectrometry（UV-vis DRS），photoluminescence spectra（PL） and electrochemical impedance spectroscopy（EIS）.The results showed that the loading of MK30 as a carrier effectively promoted the separation of C₃N₅ photoelectron-holes，and the charge transfer rate was improved.The efficient degradation of tetracycline（TC） solution was achieved under visible light irradiation for 60 min，and the degradation rate reached 97.15%.The recycled C₃N₅/MK30 photocatalyst still showed good activity.The C₃N₅/MK30 photocatalyst was coated on the surface of concrete in the form of cement coating，and the best photocatalytic activity was shown when the mass fraction was 6.5%.The C₃N₅/MK30 photocatalytic coating achieved a maximum degradation rate of 92.96% for 25 mL of TC solution with a mass concentration of 200 mg/L on the surface.The cement coating still showed a high degradation rate of 91.72% after scouring and drying by high-pressure water gun.The loading of C₃N₅/MK30 played a role of crystal nucleus to promote the hydration of cement and the formation of hydration products.The generated large amount of hydration products could effectively fill the pores，making the bonding between the concrete matrix and the cement coating closer.The compressive strength of concrete cured for 7 and 28 d was increased by 20.53% and 9.26%，respectively.

In this study，layered Li₂MnO₃ was prepared by solid-phase synthesis and applied to the photocatalytic degradation of 2，4-dichlorophenol（2，4-DCP） in water.The morphology and structure of the photocatalysts were characterized using XRD，TEM and FT-IR，and the optical and electrochemical properties were characterized through UV-Vis DRS and EIS.It was found that the Li₂MnO₃（LMO-900） obtained at a sintering temperature of 900 ℃ exhibited excellent photocatalytic performance，with a degradation efficiency of 2，4-DCP as high as 87% within 30 min.The results of ultraviolet-visible diffuse reflectance spectroscopy（UV-Vis DRS） and Mott-Schottky curves showed that the band gap of Li₂MnO₃ was 2.07 eV，the valence band potential was 1.68 V（vs.NHE） and the conduction band potential was -0.39 V（vs.NHE），indicating that it had good photogenerated electron and hole redox capabilities.Electrochemical impedance spectroscopy tests revealed the effect of sintering temperature on carrier separation efficiency，among which LMO-900 had the highest carrier separation efficiency.Radical trapping experiments showed that holes（h⁺） and superoxide anion radicals（∙O₂^-） were the main active species in the process of Li₂MnO₃ photocatalytic degradation of 2，4-DCP.Electronic structure calculation and analysis showed that the Mn-O bond was the key to the photocatalytic activity centre and played a decisive role in the degradation of 2，4-DCP.