赤泥复合物固化/稳定化镉污染土特性研究

赤泥是工业生产氧化铝产出的固体废渣,产量庞大且具有较强碱性的特点。尝试将赤泥作为碱性激发剂与粉煤灰、粒化高炉矿渣（GGBS）结合用于固化/稳定镉污染土,对养护7、14、28 d试样的无侧限抗压强度特性、剪切特性、重金属浸出特性和微观结构进行研究。研究结果表明：土中镉离子会降低土体强度,掺入赤泥、GGBS和粉煤灰后土体强度相应增强;镉离子初始浓度会对赤泥基固化土强度造成影响,当初始值高于临界浓度值,土体强度开始逐渐降低;土中镉浓度的增加会降低土体剪切强度和黏聚力,同时增大摩擦角;赤泥-GGBS固化土有较高的强度和较低的重金属浸出率,相较于赤泥-粉煤灰有更好的固化/稳定效果。     

赤泥的变形-强度特性与结构性关系的研究

制铝工业排出的大量固体废料?--赤泥具有较强的结构性,笔者对其结构性及变形–强度特性进行了研究。根据饱和原状赤泥样及扰动样固结排水三轴剪切试验资料,用土力学方法分析了变形–强度特性与结构性之间的关系,探讨了结构性参数随轴应变及固结压力变化的规律。研究表明：（1）对浸水反应比较迟钝的饱和赤泥,用三轴试验条件下各应变水平原状样与扰动样的主应力差之比所表示的结构性定量化参数,来研究结构性对变形强度的影响可以得到良好的规律性。（2）结构性参数对固结周围应力反应敏感,不同固结周围压力和剪切应力对结构性的影响,主要发生在低应变区段内。(3)赤泥的变形–强度特性与其在形成过程中的固结应力大小及龄期长短没有直接的规律性关系,而与其在物理化学作用下结构性的强弱相关。     

混合赤泥胶结特性产生机制及对其力学特性的影响试验研究

为了研究混合赤泥胶结特性产生机制,利用XRF、XRD、SEM等微观测试手段分析了混合赤泥在脱水干燥过程中化学成分、矿物组成、微观结构的变化,探讨了胶结强度随脱水龄期延长的变化规律。在此基础上,通过固结排水三轴剪切试验对5个脱水龄期混合赤泥的力学特性进行了研究,揭示了混合赤泥胶结强度的形成对其力学特性和结构性的影响。研究表明:混合赤泥的胶结强度的形成主要是因为烧结法赤泥中的水泥水硬性矿物的水化反应和活性氧化物的碳化反应形成的,并且主要集中在脱水龄期前70 d内;混合赤泥抗剪强度的增长与赤泥胶结强度的形成有直接关系,且主要体现在其黏聚力上;对具有相同初始物理指标、不同脱水龄期的混合赤泥,采用三轴试验各应变水平下不同脱水龄期干燥试样与刚出厂初始试样的主应力差之比所表示的结构性定量化参数,来研究结构性对变形强度的影响可以得到良好的规律性。     

垃圾焚烧飞灰水泥固化体强度稳定性研究

针对垃圾焚烧飞灰安全处置技术要求,采用水泥对其进行固化、稳定化处理,研究了不同水泥添加量、不同养护时间和渗沥液浸泡时间对固化体无侧限抗压强度及破坏特性的影响,并对垃圾渗沥液的侵蚀机制进行了分析。结果表明：当水泥添加量小于5%,养护时间小于3 d时,飞灰固化体在渗沥液浸泡下迅速解体,垃圾渗沥液的侵蚀对飞灰固化体的强度有较大的影响,浸泡后的固化体呈现出明显的应变软化特征,而未经浸泡的固化体的强度增长符合y=a[1-exp(-bt)]模式。随着水泥添加量及养护时间的增加,飞灰固化体无侧限抗压强度增加,破坏应变减小,而随着浸泡时间的增加,飞灰固化体的无侧限抗压强度先增大后减小,转折点大约在5～7 d,破坏应变近似呈线性增大。渗沥液对飞灰固化体的侵蚀主要是其成分抑制了固化体水化反应和破坏了水化产物。研究成果可为垃圾焚烧飞灰的安全处置技术提供理论依据和参数支持。     

稳定赤泥路用可行性与耐久性试验研究

水泥系结合料稳定赤泥应用于公路工程是消纳大宗工业固体废料赤泥的新技术路向。目前,路用稳定赤泥耐久性能的研究滞后于工程实践,为对此研究,进行稳定剂配比研究、干湿循环与冻融循环试验和微观试验。结果表明：水泥、石灰和磷石膏结合料稳定赤泥的标准强度最小为3.6 MPa,可满足路面稳定基层承载标准,且5级循环后试样质量损失趋于稳定。磷石膏比例由8%减小到2%,5级干湿循环后强度降低至1.69～3.69 MPa,强度损失率(BDR/%)达到35.1%～85.4%,5级冻融循环后强度降低至2.63～3.70 MPa,强度损失率(BDR/%)达到54.82%～79.79%,表明硫激发耦合效应的磷石膏掺量不宜超过赤泥用量的2%。此外,压汞试验研究揭示干湿与冻融循环导致试样大孔隙(直径>0.1μm)占比增加,并与强度呈显著负相关。综合承载性能与耐久性能试验,使用稳定赤泥替代公路道面水稳材料是可行的,最优配比为赤泥：水泥：石灰：磷石膏=100︰8︰2︰2。基于循环强度衰减特征,工程实践中施工期限制、早期养护质量等至关重要,且应严格控制稳定赤泥中的磷石膏掺量。     

赤泥的固结排水抗剪强度

赤泥是氧化铝厂生产氧化铝的副产品，如何处理利用是国内外十分关注的问题。目前解决这一问题的途径很多，利用赤泥筑坝是有效的方法之一。本文探讨赤泥在三轴压力作用下的变形性质，赤泥排渗固结差，孔隙比大，含水量高，容重偏低，不排水条件下测定的抗剪强度指标低，但在固结条件下则有较高的抗剪强度。     

赤泥堆场岩溶渗漏治理

渗漏问题一直是赤泥堆场的一个难题。在岩溶地区的赤泥堆场,因岩溶裂隙管道的存在,渗漏的产生是必然的,而防渗处理又是一个比较复杂、系统的工程。而对堆存强碱性(溶液的pH值≥12)液、固体物的堆场,若发生废液外渗,其对环境的危害及影响都较大。对赤泥堆场岩溶渗漏通道采取垂直帷幕注浆、场内封堵落水洞、赤泥铺盖等综合防渗措施进行治理,通过灌浆前后地层的渗透性对比和泉点水质监测,结果表明防渗治理的效果很好。     

武汉东湖淤泥早强固化试验研究

利用传统淤泥主固化材料水泥与辅助固化材料粉煤灰和石膏,通过组合配比对武汉东湖疏浚淤泥分别进行固化,基于无侧限抗压强度试验和三轴剪切试验,确定不同材料组合及配比下淤泥固化强度和特点。试验研究表明：在疏浚淤泥固化过程中水泥占主导地位,对固化效果影响最为显著;粉煤灰起到的作用相当于降低了淤泥初始含水率,表现在固化淤泥早期强度的快速提高;石膏有利于固化淤泥早期强度的形成,其作用持续于整个淤泥固化过程。随着含水率的增大,单纯水泥固化淤泥试样的应力-应变关系曲线由应变软化逐渐过渡到应变硬化模式,围压对固化淤泥强度的影响程度也随着含水率的增大而逐渐减弱,辅助固化材料的添加使原单纯水泥固化淤泥的应变硬化型曲线变为应变软化模式。不同含水率东湖疏浚淤泥固化材料最佳配比为水泥掺入比20%,粉煤灰为3倍的水泥量,石膏为30%的水泥量,该研究成果有助于武汉东湖底泥的治理以及疏浚淤泥排放场地的地基处理和环境整治。     

赤泥治理地表水体与底泥磷污染的研究进展

赤泥是制铝工业提炼氧化铝过程产生的固体废弃物。目前,全球累计排放的赤泥约40亿吨,并仍以1亿2000万吨的年排放量不断增加。赤泥现在主要依靠堆场或填海处置,不仅占用大量土地资源、耗费较多维护费用,而且对周边的生态环境造成巨大的污染,因此迫切需要进行赤泥的综合利用。由于赤泥具有颗粒分散性好、比表面积大、吸附性能优、在溶液中稳定性高等优点,近年来在污染控制与环境修复中应用广泛。本文概述了赤泥的种类、矿物组成与理化特性,总结了赤泥在控制地表污水与底泥中磷的应用研究进展,重点探讨了赤泥的不同改性方法、作用机制和除磷效果,并指出了未来可能发展的研究方向。     

固化有机质淤泥试验研究

淤泥固化技术是淤泥资源化的一个重要方法。当采用水泥基材料对有机质淤泥固化处理时,淤泥中的有机质严重影响了淤泥固化的效果。对此,笔者进行了固化有机质淤泥的试验研究,在分析有机质对淤泥固化效果影响机理的基础上,掺加不同外加剂改善有机质淤泥的固化效果,试验结果发现,碱性剂的加入会导致有机质的溶解,削弱淤泥的固化效果,粉煤灰的加入削弱了有机质对水泥水化的阻碍作用,有效提高了固化体的强度,采用水泥一粉煤灰一硫酸钠复合固化材料大幅度提高了固化淤泥的短期强度和长期强度,粉煤灰的加入提供了大量的钙离子,其掺量越大,固化淤泥无侧限强度后期增长率越大。     

铝土矿赤泥的开发利用

赤泥耕层土是一种大量消纳赤泥,同时又将其转化为二次资源的赤泥产品。该技术以农作物废弃物为改性剂,通过改性剂在赤泥中发酵腐化的产物改性赤泥成适宜植物生长的土壤。该技术应用不受赤泥组分、结构差异等因素限制,具有广泛适用性,尤其是有价金属元素含量低、又不适宜于制作建材的赤泥以及堆场防渗、防溃（堤）能力弱,需迅速消减的赤泥库的赤泥土可优先选用该技术处理。     

Stabilities of heavy metals in soils treated with red mud

This paper discussed the stabilities of heavy metals in soils treated with red mud. Soil has been polluted by heavy metals more and more seriously during recent several decades, and they are harmful to mankind and animals. The current tendency is to develop in-situ technique by using industrial processing waste as additives to stabilized heavy metals to minimize the disturbance of contaminated soils. Soil samples were collected from the Niujiaotang mining area, Guizhou Province, southwestern China. They were farmed soils polluted weakly by fly ash （QBT） and polluted badly by waste water （BXT） from smelter, respectively. One of the red mud samples （BRM） was collected from Bayer process and the other （CRM） from confederate process in the Alumina Plant of Guizhou. Free metal ion concentrations were analyzed with Donnan Membrane Technique and predicted with ECOSAT. The concentrations of free heavy metal ions in QBT increased after appending CRM, but decreased when adding BRM. The more the red mud was added, the higher the concentration would be, and the free concentrations of nickel and cadmium ions would vary more greatly than those of copper and zinc ions. When appending red muds into BXT, the free concentrations of copper and zinc ions varied little. While those of free nickel and cadmium decreased obviously at the ratio of 2.00%. The variation of the concentration was still biggish after appending BRM at the ratio of 0.50%, but smaller than that of 2.00%. The concentrations of free cadmium ions increased after adding CRM at the ratio of 0.50%. All experimental processes were modeled through ECOSAT. The predicted and measured results were consistent, except for zinc. Contributions of soil sorbents to the heavy metal adsorptions were also modeled through ECOSAT. The sorbents in soil included soil organic matter, iron hydroxides, clay and the Donnan gel of soil organic matter. Compared to the soils without red muds, no matter what kind of red mud and how much was added in soil, the contributions changed slightly.     

赤泥改性黄土的基本工程性质研究

为探究赤泥改性黄土的基本工程特性,进行无侧限抗压试验、直剪试验及渗透试验,得出赤泥改性黄土的最佳配比,建立了抗剪强度、无侧限抗压强度与电阻率的经验公式。通过动三轴试验,分析了循环动荷载下改性黄土的累积塑性变形、动弹性模量及浸出毒性。结果表明,随赤泥含量增加,改性黄土无侧限抗压强度和黏聚力都先增大后减小,当赤泥含量为15%时其28 d无侧限抗压强度达到3.5 MPa,较不掺入赤泥时提高约34.7%;改性黄土的渗透系数随赤泥含量增加先快速降低,至赤泥含量5%后趋于稳定;改性黄土的抗剪强度、无侧限抗压强度与电阻率呈良好的线性关系;改性黄土在循环动荷载下的临界动应力达600 kPa,最大动弹性模量比未改性黄土高出6倍,且其浸出液不具有浸出毒性。     

Reduction of phosphorus release from high phosphorus soil by red mud

The high phosphorus levels cause the release of phosphorus from soils, thereby increasing the potential for phosphorus export to adjacent water bodies. The loss of phosphorus from soils to surface waters is a major source of water quality impairment. Therefore, soil phosphorus immobilization seems necessary. In this study, red mud (RM) was employed to immobilize phosphorus in a typical agricultural soil. It was found that phosphorus was effectively immobilized by RM. Batch leaching experiments showed that RM reduced phosphorus release from 14.38 to 2.56 mg/kg when soil was amended with 1% RM. Column leaching experiments showed that RM reduced the total amount of phosphorus released from 36.73 to 18.79 mg/kg during the investigated period. Sequential chemical extraction results indicated that RM amendment transformed H₂O-P into more stable fractions. The results suggested that application of RM amendment to soils could significantly immobilize soluble phosphorus, reducing phosphorus release to the environment.     

赤泥中的稀土资源:分布、赋存和提取

铝土矿中通常含有一定量的稀土元素(REE),氧化铝生产过程导致矿石中几乎所有的REE都富集到赤泥中,其中喀斯特型铝土矿所产生赤泥中的REE含量相对更高,是潜在的REE二次资源,综合利用赤泥中的REE己成为研究热点之一.已有的研究表明,REE分布于赤泥的各个矿物相,包括铝土矿保留下来的矿物相或新形成的矿物相.类质同象可能是其中REE的主要赋存形式,含Fe或Ti的矿物是其主要载体矿物,存在少量REE独立矿物,硅酸盐矿物相或新形成的矿物相也是REE潜在载体矿物.目前,赤泥中REE回收利用多处于实验室研究阶段,包括直接酸浸、焙烧浸出和生物浸出等方法.对比结果表明,直接酸浸和焙烧浸出是有效的赤泥回收REE的方法,但难点是如何增加浸出的选择性,及简化工艺流程.此外,生物浸出的过程更绿色环保,可能成为未来最具前景的回收REE的方法.在回收过程中,设计和发展多元素回收工艺,将Fe、Al、Na、Ti和REE等元素均纳入提取回收流程,并将有用金属回收后所产生的残渣作为制备建筑装饰、催化支撑材料、吸附剂等的原材料,将是赤泥综合利用未来发展方向.     

赤泥中氟迁移转化的影响因素分析

为了研究赤泥中氟向下运移过程中的影响因素,根据堆场周围的水文地质条件,设计了7组动态淋溶试验,并对试验数据进行了灰色关联度分析。结果表明,排放7天后的赤泥其表面下700 mm处的温度仍达78℃,而刚排放到堆场的冲灰水温度更高,可达87.5℃,高温赤泥和冲灰水有利于氟的迁移;赤泥的pH值为10.29～11.83,浸出液的pH值为12.00～13.20,碱性很大,致使氟易随水迁移;赤泥的其它污染组分,如总硬度、Cl-、SO42-、K+、Na+、Ca2+、Mg2+,均对氟的迁移有一定的影响,且Na+、SO42-和Ca2+为主要控制因素,即溶液中Na+、SO42-、Ca2+含量越高,赤泥中的F-离子越易淋出。      

Evaluation of chemical immobilization treatments for reducing arsenic transport in red mud

Red mud (RM) was produced during alumina production from bauxite known as the Bayer process. Arsenic was detected in the solid phase of RM (RMsf) which was disposed in the disposal area. This study investigates the effectiveness of using Zero-valent iron (ZVI), ferrihydrite, ferrous sulfate (FeSO₄), waste acid (WA) or CO₂ for immobilization of arsenic in the RMsf. To test the effect of the amendments on the arsenic leachability, the RMsf samples were amended with the iron-based materials or acidifiers at various w/w (weight/weight) ratios (1–10 %) for 30 days. The leachability of arsenic in the RMsf was evaluated by a 4-step water elusion process. After 30-day treatment of the RMsf, the leachability of As decreased from an initial (12.7 %) to (7.0 %) with a w/w ratio of 5 % ZVI (0 %) with 5 % FeSO₄·7H₂O, (3.4 %) with 5 % ferryhydrite, (2.0 %) with 6 % WA and (11.8 %) with 6 % CO₂. FeSO₄·7H₂O and WA showed more effectively than other amendments for immobilizing arsenic. Arsenic fractionation with a sequential extraction procedure was used to evaluate the arsenic migration potential in the RMsf. FeSO₄ and WA were effective in increasing the hydrous oxide combined arsenic in the RMsf. The leachable Cl^? and SO₄ ^2? in the RMsf increased from 2.9 to 14.1 mg/g and 19.9–44.4 mg/g with 6 % WA and 5 % FeSO₄·7H₂O added, respectively. The estimated cost of the FeSO₄ and WA treatment was 0.47 and 0.49 USD per ton, respectively.     

Chemical and environmental compatibility of red mud liners for hazardous waste containment

Red mud residue from alumina production has been proposed as an alternative liner material. The chemical and environmental compatibility of red mud upon exposure to representative organic (methanol, heptane, TCE, and acetic acid) and inorganic liquids (CaCl₂ and seawater) was studied. Chemical compatibility assays comprised Atterberg limits and sedimentation and hydraulic conductivity tests for red mud interacted with the chemical liquids, whereas the environmental compatibility was assessed through the leaching of metals from red mud as permeated with the liquids. Methanol greatly reduced the plasticity at concentrations ≥80 % by volume, but it did not increase the hydraulic conductivity of compacted red mud. High concentrations (≥60 % v/v) of acetic acid reduced the plasticity and enhanced the sedimentation of red mud. Conversely, acetic acid concentrations ≤40 % caused dispersion, but damaged the hydraulic properties and structure of red mud. The percolation of a pH 2 acetic acid solution did not adversely affect the hydraulic performance of the red mud liner. Neither diluted heptane nor TCE affected the red mud. However, pure organics suppressed the plasticity and induced aggregation of red mud, suggesting a great detrimental effect on red mud liners. The red mud exhibited great resistance to attack by inorganic salt solutions. Some concerning leaching of metals (primarily Al and Cr) occurred as water, acetic acid, and CaCl₂ solutions percolated through red mud, but effluent metals concentration quickly dropped to permissible levels. In general, red mud exhibited a high resistance against chemical attack; nevertheless, exposure to low-dielectric-constant organic chemicals should be avoided.