Acid precipitation coupled electrodialysis to improve separation of chloride and organics in pulping crystallization mother liquor

Inefficient separation of inorganic salts and organic matters in crystallization mother liquor is still a problem to industrial wastewater treatment since the high salinity significantly impedes organic pollutant degradation by oxidation or incineration. In the study, acidification combined electrodialysis (ED) was attempted to effectively separate Cl^- ions from organics in concentrate pulping wastewater. Membrane's rejection rate to total organic carbon (TOC) was 85% at wastewater intrinsic pH=9.8 and enhanced to 93% by acidifying it to pH=2 in ED process. Negative-charged alkaline organic compounds (mainly lignin) could be liberated from their sodium salt forms and coagulated in acidification pretreatment. Neutralization of the organic substances also made their electro-migration less effective under electric driving force and in particular improved separation efficiency of chloride and organics. After acid-ED coupled treatment (pH=2 and J=40 mA·cm^-2)[TOC] remarkably reduced from 1.315 g·L^-1 to 0.048 g·L^-1 and[Cl^-] accumulated to 130 g·L^-1 in concentrate solution. Recovery rate of NaCl was 89% and the power consumption was 0.38 kW·h·kg^-1 NaCl. Irreversible fouling was not caused as electric resistance of membrane pile maintained stably. In conclusion, acidic-ED is a practical option to treat salinity organic wastewater when current techniques including thermal evaporation and pressure-driven membrane separation present limitations.     

Systematic study of H2 production from catalytic photoreforming of cellulose over Pt catalysts supported on TiO2

Hydrogen (H₂) production from photocatalytic reforming of cellulose is a promising way for sustainable H₂ to be generated. Herein, we report a systematic study of the photocatalytic reforming of cellulose over Pt/m-TiO₂ (i.e. mixed TiO₂, 80% of anatase and 20% of rutile) catalysts in water. The optimum operation condition was established by studying the effect of Pt loading, catalyst concentration, cellulose concentration and reaction temperature on the gas production rate of H₂ (r_H2) and CO₂ (r_CO2), suggesting an optimum operation condition at 40 ℃ with 1.0 g·L^-1 of cellulose and 0.75 g·L^-1 of 0.16-Pt/m-TiO₂ catalyst (with 0.16 wt% Pt loadting) to achieve a relatively sound photocatalytic performance with rH₂ = 9.95 μmol·h^-1. It is also shown that although the photoreforming of cellulose was operated at a relatively mild condition (i.e. with an UV-A lamp irradiation at 40 ℃ in the aqueous system), a low loading of Pt at ~0.16 wt% on m-TiO₂ could promote the H₂ production effectively. Additionally, by comparing the reaction order expressed from both r_H2 (a₁) and rCO₂ (a₂) with respect to cellulose and water, the possible mechanism of H₂ production was proposed.     

粉煤灰酸法提取氧化铝蒸发母液回收氯化铝工艺研究

在粉煤灰盐酸法提取氧化铝蒸发结晶工序中,由于氯化铝溶液多次循环蒸发,引起蒸发母液中钙、镁、硅、磷等杂质离子的富集,当母液中杂质离子的浓度达到一定程度时需将部分氯化铝蒸发母液外排,这将会造成15%~20%原料铝的损失。利用氯化氢气体盐析结晶技术对蒸发母液进行处理,通过两级盐析结晶和浓盐酸洗涤,不仅实现了回收蒸发母液中氯化铝的目的,还提高了六水氯化铝晶体的纯度,使回收的氧化铝纯度达到99.38%,同时氧化铝中氧化钙、氧化镁、五氧化二磷的质量分数分别降低至2.680×10^-5、2.849×10^-4、2.051×10^-4。提出了蒸发母液回收氯化铝工艺路线,此流程可完全并入现有粉煤灰盐酸法提取氧化铝工艺的主流程。     

利用电解锰渣制备As(Ⅲ)吸附材料及其性能研究

通过对工业废弃物电解锰渣(electrolytic manganese residues, EMRs)进行改性制备As(Ⅲ)吸附材料（改性EMRs），探究了NaOH用量、超声及微波对其表面结构及吸附性能的影响。结果表明：该工业废渣在固液比M(EMRs)∶V(NaOH, aq) = 1∶10(C _NaOH，aq = 2.0 mol·L^-1)条件下，经超声反应（200 W）2 h脱除大部分Si、S、Ca后，再微波（700 W）反应5 min以使Fe、Mn等活性吸附基团在其表面沉积，最后经105℃烘干制得改性EMRs。SEM结果表明，EMRs改性后表面形成片层纳米结构，对砷具有良好的吸附性能，可将初始As(Ⅲ)浓度为50 mg·L^-1废水出水中砷降至0.042 mg·L^-1，符合国家地表水环境质量标准Ⅰ类水质量要求(GB 3838—2002)；同时，经3% NaOH溶液再生处理后可继续使用。XPS结果表明，改性EMRs吸附砷性能与其表面Fe₃O₄、FeOOH、MnO₂等对As(Ⅲ)具有吸附作用或氧化作用的活性物种的增多密切相关。     

Membrane enhanced COD degradation of pulp wastewater using Cu2O/H2O2 heterogeneous Fenton process

Both activity and stability of the catalyst can be improved in heterogeneous Fenton reaction, in particular, with no limitation for the working pH and no production of the sludge. In this work, a combination of catalyst Cu₂O and pore-channel-dispersed H₂O₂ is proposed to treat the pulp wastewater. Degradation degree of CODs in the wastewater was up to 77% in the ceramic membrane reactor using Cu₂O powder (2.0 g·L^-1) and membranefeeding H₂O₂ (0.8 ml·L^-1) within 60 min. Evolution of ·OH radical formation in the advanced oxidation process was analyzed with a fluorescent method. Utilization efficiency of H₂O₂ was successfully enhanced by 10% with the membrane distributor. Further on, the catalyst recyclability was evaluated in a five-cycle test. The concentration of copper ions being dissolved in the treated water was monitored with ICP. After Cu₂O/H₂O₂ (membrane) treatment the effluent is qualified to discharge with COD concentration lower than 15 mg·L^-1 with regard to the national standard GB25467-2010.     

改性活性半焦吸附-Fe/C微电解-Fenton联用技术处理焦化废水

采用改性活性半焦吸附-Fe/C微电解-Fenton联用技术处理焦化废水,探究联用技术工艺参数对焦化废水化学需氧量(COD)去除率的影响,结果表明:(1) 针对Fe/C微电解处理焦化废水的最佳操作条件为:pH=3,Fe与C质量比2.0∶1,Fe/C投加量30 g·L^-1,反应时间60 min,反应温度35 ℃;(2) 采用Fe/C微电解-Fenton氧化处理焦化废水最佳操作条件为:过氧化氢投加量25 mL·L^-1,pH=3,Fe与C质量比2.0∶1,Fe/C投加量30 g·L^-1,反应时间8 h。在最佳吸附-Fe/C-Fenton联用工艺条件下操作,对焦化废水COD降解率达到85.23%,COD由199.27 mg·L^-1降至29.43 mg·L^-1。动力学研究表明,动力学方程能很好的拟合Fe/C微电解降解过程。     

2-Ethyl-9,10-anthraquinone assisted sol–gel synthesis of Pd/γ-Al_2O_3 nanorods with enhanced catalytic performance in 2-ethyl-9,10-anthraquinone hydrogenation

A series of nanorod-like porous Pd/γ-Al_2 O_3 catalysts with controllable textural properties and enhanced catalytic performance in 2-ethyl-9,10-anthraquinone(eAQ) hydrogenation for H_2 O_2 preparation were successfully prepared via a facile sol-gel method using aluminum isopropoxide as aluminum precursor and eAQ as structure directing agent,sequential calcination and impregnation process with Na_2 PdCl_4 solution.The physicochemical properties of the catalysts obtained with different addition amounts of eAQ.were comparatively characterized by XRD,TG-DSC,BET,TEM,CO-TPR,H_2-TPR and H_2-O_2 titration.The results show that addition of eAQ can not only effectively control the textural properties(surface area,pore volume and average pore size) of the catalysts,but also lower their reduction temperature of active metal.Importantly,the catalyst obtained with an addition amount of 4 wt% eAQ shows the highest hydrogenation efficiency of 10.28 g·L~(-1),which is 37.3% higher than 7.49 g·L~(-1) of the catalyst obtained without eAQ.     

Synthesis of hierarchical dendritic micro–nano structure ZnFe_2O_4 and photocatalytic activities for water splitting

Hierarchical dendritic micro–nano structure Zn Fe_2O_4 have been prepared by electrochemical reduction and thermal oxidation method in this work. X-ray diffractometry, Raman spectra and field-emission scanning electron microscopy were used to characterize the crystal structure, size and morphology. The results show that the sample(S-2) is composed of pure ZnFe_2O_4 when the molar ratio of Zn~(2+)/Fe~(2+)in the electrolyte is 0.35. Decreasing the molar ratio of Zn~(2+)/Fe~(2+), the sample(S-1) is composed of ZnFe_2O_4 and α-Fe_2O_3, whereas increasing the molar ratio of Zn~(2+)/Fe~(2+), the sample(S-3) is composed of ZnFe_2O_4 and Zn O. The lattice parameters of ZnFe_2O_4 are influenced by the molar ratio of Zn~(2+)/Fe: Zn at excess decreases the cell volume whereas Fe at excess increases the cell volume of Zn Fe_2O_4. All the samples have the dendritic structure, of which S-2 has micron-sized lush branches with nano-sized leaves. UV–Vis diffuse reflectance spectra were acquired by a spectrophotometer. The absorption edges gradually blue shift with the increase of the molar ratio of Zn~(2+)/Fe~(2+). Photocatalytic activities for water splitting were investigated under Xe light irradiation in an aqueous olution containing 0.1 mol·L~(-1)Na_2S/0.02 mol·L~(-1)Na_2SO_3 in a glass reactor. The relatively highest photocatalytic activity with 1.41 μmol·h-1· 0.02 g~(-1)was achieved by pure ZnFe_2O_4sample(S-2). The photocatalytic activity of the mixture phase of Zn Fe_2O_4 and α-Fe_2O_3(S-1) is better than ZnF e_2O_4 and ZnO(S-3).     

微波-过氧化氢工艺处理含Cu-EDTA废水

采用微波-过氧化氢工艺处理含Cu-EDTA废水,考察反应时间、初始pH、H₂O₂投加量、微波功率以及共存物质等因素对该工艺处理效能的影响,并分析了氧化作用机制。结果表明,在初始pH为3,H₂O₂投加量为41 mmol·L^-1,微波功率为210 W时,1.57 mmol·L^-1Cu-EDTA反应10 min后,Cu和TOC去除率分别高达97.0%和60.7%,出水电导率低至1.8 mS·cm^-1,产泥量仅为0.15 g·L^-1。NO₃^-的存在对Cu-EDTA的氧化降解过程无明显影响,而Cl^-、H₂PO₄^-和酒石酸对反应过程有一定的抑制作用。该工艺下反应4 min后Cu-EDTA基本氧化为中间产物,并在4～6 min内急剧降解,最终形成小分子羧酸类物质、NH₃-N和无机碳。反应过程沉淀产物主要以CuO形式存在。相比Fenton工艺,该工艺在氧化效能、出水电导率及产泥量等方面有显著优势。     

Direct synthesis of single-phase α-CaSO4·0.5H2O whiskers from waste nitrate solution

Single-phase α-CaSO₄·0.5H₂O whiskers were directly synthesized from waste Ca(NO₃)₂ solution using a hydrothermal method, and HNO₃ was synchronously regenerated. The effects of reaction temperature and Ca²⁺ concentration on the phase composition and morphology of products were determined by X-ray diffraction and optical microscopy. On the basis of the experimental results, the formation diagram of α-CaSO₄·0.5H₂O was plotted within the range of 5-35 g·L^-1 Ca²⁺ and 115℃-150℃. In addition, the conditions of the direct synthesis of α-CaSO₄·0.5H₂O were determined. Well-crystallized, single-phase α-CaSO₄·0.5H₂O whiskers with high aspect ratios (length, 1785 μm; diameter, 10.63 μm; aspect ratio, 168) and HNO₃ (70.25 g·L^-1) were obtained at the optimal conditions of 25 g·L^-1 Ca²⁺ and 125℃.     

Fe/Al_2O_3催化剂催化氧化兰炭废水

采用浸渍法制备Fe/Al_2O_3催化剂,采用BET、XRD和穆斯堡尔谱等进行结构和性能表征。以自制Fe/Al_2O_3为催化剂,应用催化湿式过氧化氢氧化技术处理COD为6 742 mg·L-1的兰炭废水,通过建立正交实验确定最佳实验条件,结果表明,在p H=4、过氧化氢添加量9.6 m L、反应时间150 min和反应温度80℃条件下,兰炭废水COD去除率达66.30%。对催化氧化后的废水进行GC-MS分析,确定最终氧化产物主要为乙酸。表明自制Fe/Al_2O_3催化剂具有优良的催化效果,并使大分子难降解有机污染物分解为易生化的小分子污染物,甚至被完全分解矿化。     

Separation of mixed salts(Cl~-/SO_4~(2-)) by ED based on monovalent anion selective membranes

The industrial products or wastewater rich in the mixed salts(Cl~-/SO_4~(2-)) not only causes the environmental damage, but also induces waste of resource. In this study, an ED stack with monovalent selective AEMs and conventional CEMs was employed to separate the Cl~-and SO_4~(2-)from simulated wastewater. The effect of current density and mass fraction percentage was investigated in order to optimize the experimental conditions during ED process. It was found that at a concentration ratio between NaCl and Na_2SO_4 of 95/5(wt%/wt%) and a current density of40 m A·cm~(-2), a current efficiency of 72%, an energy consumption of 1.6 k W·h·kg~(-1) Na Cl and a Cl~-/SO_4~(2-)concentration(67.5/3.5 g·L~(-1)) were obtained. Hence, it is appropriate and effective to separate Cl~-and SO_4~(2-)by ED using the monovalent selective AEMs.     

Methane hydrate crystal growth on shell substrate

Hydrate crystals growth on the surface of methane bubble (hydrate film) in pure water was studied by using a high-pressure visible microscope under the conditions of subcooling ΔT = 5.44–13.72 K and methane concentration difference ΔC = 2.92–8.19 mol·L^-1. It was found the hydrate film is porous and the hydrate crystals grow towards the liquid phase on the film substrate. The crystal morphology and growth rate are affected by ΔT and ΔC. When ΔT < 8.82 K and ΔC < 4.12 mol·L^-1, the hydrate grows into scattered columnar crystals, and the axial growth rate of the crystal gradually decreases. When ΔT > 8.82 K or ΔC > 4.12 mol·L^-1, the hydrate crystals grow in dendritic shape, and the axial growth rate increases first and then decreases. The perimeter and area of the growing hydrate crystals were measured, and the fractal dimension of hydrate crystal under different ΔC and ΔT was calculated. The results show that the fractal dimension of columnar hydrate crystal is greater than 3. When 3.87 mol·L^-1 < ΔC < 4.20 mol·L^-1 and 7.4 K < ΔT < 8.8 K, the fractal dimension of columnar hydrate crystal is greater than 4; The fractal dimension of dendritic hydrate crystal is less than 3. When ΔC > 4.77 mol·L^-1, ΔT < 8.52 K, the fractal dimension of dendritic hydrate crystal is less than 2.     

磷酸脲母液制备工业级磷酸二氢铵工艺研究

湿法磷酸制备磷酸脲过程中会副产大量磷酸脲母液,母液含有金属杂质及五氧化二磷含量较高。采用溶剂萃取法回收磷酸脲母液中五氧化二磷制备工业级磷酸二氢铵（MAP）,分别考察了包括萃取、洗涤、中和、精制、结晶等工艺流程对产品收率及纯度的影响,确定了最佳工艺条件：萃取相比（有机相与水相体积比）=3:1,萃取时间为5 min,萃取温度为50 ℃,洗涤相比（有机相与洗涤剂体积比）=10:1,中和pH为4.5,复合酸性萃取剂PO8皂化率为20%,精制相比（萃取剂与水相体积比）=1:1,浓缩比为1.36,结晶温度为30 ℃。在该条件下制备的工业级MAP纯度可达99.45%,母液中五氧化二磷回收率为85.34%。该工艺对环境友好,原料中五氧化二磷回收率高,具有较高的经济效益。     

反应结晶过程中二水硫酸钙晶粒性能

设计了CaHPO₄·2H₂O-H₂SO₄-H₃PO₄-H₂O体系结晶温度、液相SO₄^2-含量、液相P₂O₅含量、搅拌速率和结晶时间的五因素四水平正交实验,通过测量晶体平均粒径优化出平均粒径最大的工艺参数:结晶温度80℃、液相SO₄^2-含量50g·L^-1、液相P₂O₅含量260g·L^-1、搅拌速率50r·min^-1和结晶时间2h。在该工艺参数下进行结晶过程研究,通过分析液相SO₄^2-浓度和P₂O₅浓度,XRD、SEM、EDS和激光粒度分析仪表征晶体,研究发现:0~40min为反应阶段,平均粒径减小;40min之后结晶过程遵从Ostwald递变法则,从CaSO₄·0.5H₂O过渡到CaSO₄·2H₂O,平均粒径几乎不变。     

聚丙烯酸钠包覆Fe3O4磁性交联聚合物的制备及其对Pb(Ⅱ)和Cd(Ⅱ)的吸附性能

采用溶液分散聚合和Ca²⁺表面交联制备了聚丙烯酸钠包覆Fe₃O₄的磁性交联聚合物（CPAANa@Fe₃O₄）,对其进行了XRD、FT-IR、SEM和TGA等表征。以CPAANa@Fe₃O₄为吸附剂研究了CPAANa@Fe₃O₄对水溶液中Pb²⁺、Cd²⁺的静态吸附,考察了溶液pH、吸附剂投加量、金属离子初始浓度对吸附的影响。结果表明：CPAANa@Fe₃O₄在pH 2～6范围内均具有较好的吸附性能,当吸附剂投加量分别为1.0 g·L^-1和1.6 g·L^-1时对初始浓度分别为200 mg·L^-1的Pb²⁺和100 mg·L^-1的Cd²⁺的去除率达到最大,可使Pb²⁺实现达标排放（GB 8978-1996）;CPAANa@Fe₃O₄对Pb²⁺和Cd²⁺的吸附动力学符合准二级模型,吸附等温线符合Langmuir模型,对Pb²⁺和Cd²⁺的最大吸附量分别为454.55 mg·g^-1和275.48 mg·g^-1。将CPAANa@Fe₃O₄用于处理实际电解矿浆废水,发现能有效吸附其中的Pb²⁺和Cd²⁺,具有潜在实用价值。     

H2O2强化光催化处理苯胺化工废水的应用试验

研究者在苯胺模拟废水高级氧化处理方面开展了很多研究,但针对炼化企业苯胺装置废水含盐高、色度高、COD降解难等问题尚未开展工程应用。为解决苯胺生产废水的实际问题,本研究开展了TiO₂/UV-H₂O₂氧化降解苯胺废水（1~2m³/h）的现场试验研究。考察了苯胺废水在单独TiO₂/UV、单独H₂O₂氧化及TiO₂/UV-H₂O₂协同作用下的处理效果,提出了苯胺废水的最佳处理工艺方案,并进行了成本核算。结果表明,单独TiO₂/UV和单独H₂O₂氧化对苯胺废水的脱色率和COD去除率偏低,而TiO₂/UV-H₂O₂协同作用时苯胺废水脱色率和COD去除率可达95%以上。协同氧化体系中,H₂O₂的氧化降解作用显著,H₂O₂投加量1%~2%;酸性条件利于苯胺废水的降解,特别是pH=3.8~4.2时;TiO₂/UV和H₂O₂协同作用一段时间后,停止UV而凭借残余H₂O₂可以将体系中的中间产物继续降解直至矿化成CO₂。TiO₂/UV- H₂O₂协同处理炼化企业苯胺生产废水,出水COD≤60mg/L,色度≤20倍,单位能耗约18.44kW·h/m³,明显低于文献报道值,具有显著的技术性与经济性。     

天然磁铁矿/UV/S2O82-对焦化废水中不同种类有机物的去除特性

以过硫酸盐（PS）为中心建立了C（天然磁铁矿）/PS、UV/PS、C/UV/PS氧化体系,分别对焦化废水生化出水进行深度处理,采用超滤膜法和有机物树脂分离方法分别对深度处理前后废水中有机物分子量分布特性及亲疏水性有机物含量变化进行了研究。研究表明：生化出水中含有较多的难降解芳香性有机物,且以分子量（M_W）<1×10³的低分子量有机物为主,其次是M_W>100×10³和10×10³～100×10³的大分子有机物。疏水酸和疏水中性组分是废水中的主体有机物,其DOC分别占总DOC的45.88%和32.09%。C/UV/PS相对C/PS、UV/PS氧化效果更好,在原水pH,铁矿石和PS的投加量分别为3 g·L^-1和2 g·L^-1,紫外光照射功率为300 W条件下,氧化90 min时COD、UV₂₅₄、DOC和色度的去除率分别为74.9%、93.5%、84.1%和80.1%。从矿化效果来看,C/UV/PS氧化体系对M_W>10×10³的大分子有机物的去除效果显著,深度处理后M_W<1×10³的有机物分子占比增加;该体系对疏水性和弱疏水性有机物去除效果较高,深度处理后亲水性有机物占比增加。     

内循环式铁碳微电解/H2O2耦合工艺处理多晶硅有机废水

针对铁碳微电解反应中填料易板结及处理效率低等问题,通过增加内循环装置改进反应器结构,同时将铁碳微电解与H₂O₂进行工艺耦合,用于处理多晶硅有机废水,考察了Fe-C投加量、初始pH值、H₂O₂投加量、反应时间等工艺条件对COD去除率的影响,并通过响应面法优化了工艺条件。结果表明,各工艺条件对多晶硅有机废水COD去除效果的影响大小为：铁碳投加量>反应时间>H₂O₂投加量>初始pH值,其最适宜工艺条件为：铁碳投加量250 g·L^-1,初始pH值2.8,H₂O₂投加量112 mL·L^-1,反应时间83 min,该反应条件下COD的去除率为71.26%。铁碳/H₂O₂降解多晶硅有机废水COD的动力学回归方程为Y=0.5273X-0.6347,降解COD的速率常数为0.527 3 min^-1。     

Sulfur resource recovery based on electrolytic manganese residue calcination and manganese oxide ore desulfurization for the clean production of electrolytic manganese

An environmentally friendly and resource-conserving route to the clean production of electrolytic manganese was developed, in which the electrolytic manganese residue(EMR) was initially calcined for cement buffering;then the generated SO_2-containing flue gas was managed using manganese oxide ore and anolyte(MOOA) desulfurization; at last, the desulfurized slurry was introduced to the electrolytic manganese production(EMP). Results showed that 4.0 wt% coke addition reduced the sulfur of calcined EMR to 0.9%, thereby satisfying the cement-buffer requirement. Pilot-scale desulfurization showed that about 7.5 vol% of high SO_2 containing flue gas can be cleaned to less than 0.1 vol% through a five-stage countercurrent MOOA desulfurization. The desulfurized slurry had 42.44 g·L~(-) Mn~(2+) and 1.92 g·L~(-1) S_2 O_6~(2-), which was suitable for electrowinning after purification, and the purity of manganese product was 99.93%, satisfy the National Standard of China YB/T051-2015.This new integrated technology fulfilled 99.7% of sulfur reutilization from the EMR and 94.1% was effectively used to the EMP. The MOOA desulfurization linked the EMP a closed cycle without any pollutant discharge, which promoted the cleaner production of EMP industry.