烧结法赤泥的强度演化规律

筑坝堆存是现在处理赤泥的主要方式,为了堆场安全继续向上堆载,对烧结法赤泥强度的演变规律进行了研究。通过对比不同深度处赤泥的抗剪强度,表明赤泥强度的形成与堆载时间没有必然的联系;再通过对新进场的赤泥进行强度追踪,得到赤泥强度形成过程中抗剪强度与滤水固结时间的关系曲线,从时间因素上为赤泥的安全堆载提供一个理论依据。     

赤泥在控制沉积物磷释放中的应用研究

利用烧结法赤泥中富含Ca、Fe等金属元素的氧化物而具有吸附性的特点，通过室内模拟研究赤泥投加对沉积物中各种磷形态含量及分布比例的影响，进而探讨利用赤泥控制沉积物中磷释放的可行性。对经过处理后的沉积物磷形态分析后表明，投加赤泥能促使沉积物中铁铝磷向钙磷转化（Pearson相关分析，r=-0.892，P<0.01，n=9），且赤泥的强碱性使沉积物pH值逐渐升高。确定了赤泥最佳投加比例为5%，此时沉积物的pH为9.03，铁铝磷含量由初始的148 mg/kg降至107 mg/kg，占总磷比例也由18.1%降至13.4%，钙磷含量由486 mg/kg升至546 mg/kg，其占总磷比例则由60%增至68.7%，铁铝磷和钙磷之间的转化已基本完成，继续增加赤泥投加量对沉积物中磷形态间的相互转化影响甚微。由于铁铝磷较钙磷活性高而易释放，可见投加赤泥能降低沉积物中磷的释放风险。赤泥可以作为吸附材料被应用于沉积物磷污染控制技术中，为有效控制水体内源磷负荷提供一种新思路和廉价材料。     

炼铝工业废渣生产硅灰石的拟议

一、问题的提出氧化铝生产过程的实质,简言之,就是分离去除铝土矿中的主要有害杂质 SiO_2。拜尔法生产氧化铝时 SiO_2成 Na_2O·Al_2O_3·1.7SiO_2·nH_2O进入残渣;烧结法生产氧化铝时 SiO_2则成 2CaO·SiO_2进入残渣。铝土矿中次要有害杂质 Fe_2O_3不溶于碱液介质而一道析出,泥渣外表呈赤色,故称赤泥。每生产一吨 Al_2O_3排放赤泥1.5～2吨,全国每年排放赤泥量150万吨。我厂自1954年投产以来,已堆积赤泥1000万吨左右,占地800余亩,赤泥堆高达35米,并以年增1米的速度还在升高。巨量的赤泥堆放,不仅占用大片农田,且赤泥水份大,含碱高,     

不同含水率条件下拜耳法赤泥强度及水力学特性

在利用XRD、XRF、SEM等微观测试手段分析了拜耳法赤泥的化学成分、矿物组成和微观结构的基础上,通过无侧限抗压强度实验、固结排水三轴剪切实验研究了拜耳法赤泥在不同水力路径条件下其强度特性的变化规律;同时通过非饱和土瞬态水力特性循环实验系统对拜耳法赤泥的水力学特性进行了研究。研究表明:含水率的变化对拜耳法赤泥的强度特性有较大程度的影响,在脱水干燥过程中,其抗压强度和抗剪强度指标均有较大程度的增长;拜耳法赤泥具有遇水崩解现象,已干燥硬化的赤泥会遇水崩解,强度指标明显降低,且在较低应变处即发生脆性破坏;拜耳法赤泥的土-水特征曲线和渗透系数特征曲线均展现出明显的滞后效应,说明拜耳法赤泥对水有较大的敏感性,在降雨条件影响下,拜耳法赤泥堆体的稳定性有一定程度的降低。     

赤泥的土壤化改良研究进展综述

赤泥是氧化铝生产过程中产生的固体废弃物，年产量和堆存量大，理化性质极端，严重威胁赤泥堆场周边生态环境和居民健康。赤泥土壤化改良和堆场生态修复被认为是最有希望解决赤泥问题的方法之一。对赤泥的基本理化性质，赤泥土壤化改良机理、改良措施(基质改良、植物修复和微生物修复等)及其存在问题、改良过程中的潜在生态环境风险等进行了研究和总结分析，并对赤泥土壤化改良领域未来的研究工作进行了展望和建议。     

复合赤泥在高浓度含磷废水处理中的应用

赤泥与石灰粉（CaO和Ca（OH）₂）按不同比例混合制成复合赤泥，通过投加实验考察了复合赤泥的除磷效果。结果证明，对于磷酸盐浓度为45 000 mg/L左右（以P计）的酸性工业废水，复合赤泥（赤泥与Ca（OH）₂按质量比1：1混合）投加量为240 g/L，去除率为99.97%；对于10 mg/L左右的含磷废水，赤泥的最佳投加浓度为15 g/L，上清液磷浓度可降至0.30 mg/L，出水低于0.5 mg/L的排放标准。根据以上研究结果，提出了对高浓度酸性磷酸盐废水的处理宜采用复合赤泥再加原状赤泥的二级处理方法。     

不同工况条件混合赤泥力学特性变化规律

在利用常规土工实验和XRF、XRD、SEM等微观测试手段分析了刚出厂混合赤泥化学成分、矿物组成、微观结构的基础上,通过无侧限抗压强度实验和固结排水三轴剪切实验对自然风干、浸水饱和、非饱和-饱和干湿循环3种工况条件下混合赤泥不同龄期力学特性的变化规律进行了研究。结果表明,自然风干试样的无侧限抗压强度和粘聚力要明显大于相同龄期浸水饱和试样和干湿循环试样,说明混合赤泥的强度形成与滤水过程有一定联系,且其强度的增长均主要集中在脱水龄期前70天内;混合赤泥在3种不同工况条件下无侧限抗压强度和粘聚力均有一定程度的增长,说明混合赤泥可在浸水环境下生成不可逆增长的具有水硬性的胶结矿物,使其在水环境中不发生崩解,可保证混合赤泥堆体在自然堆存过程中其力学特性满足安全堆载要求。     

拜耳法赤泥还原焙烧工艺及产物性质分析

采用正交实验,考察焙烧温度、焙烧时间、还原剂和添加剂用量对拜耳法赤泥还原焙烧效果的影响。结果表明,在焙烧温度为1 080℃,焙烧时间为70min,赤泥、还原剂、添加剂质量比为100∶9∶7的最优条件下还原焙烧赤泥,经过磁选,赤泥中的含铁矿物得到富集,精矿品位平均为67.36%,回收率平均为85.54%。用热重(TG)/差示扫描量热(DSC)分析、扫描电子显微镜(SEM)分析、X射线衍射(XRD)分析以及质量磁化率测定等方法,对赤泥还原焙烧前后的理化特性进行研究,证实经过还原焙烧,赤泥中Fe_2O_3转化为Fe_3O_4和Fe。     

添加堆肥和赤泥对土壤生物有效性Cd和Zn的影响

采用土壤培养实验，研究添加堆肥和赤泥对土壤中Zn和Cd生物有效性的影响。结果表明，单独添加堆肥或赤泥以及赤泥和堆肥一起添加到土壤，均可以降低土壤中的交换态Cd和Zn含量以及生物有效态Zn和Cd含量。与对照相比，培养1~3个月后，单独添加堆肥、单独添加赤泥和同时添加赤泥与堆肥导致土壤交换态Cd含量分别降低14%~18%、33.3%~46.1%和44.2%~57.7%；土壤交换态Zn含量分别降低54.4%~59%、100%和100%；土壤生物有效态Cd含量分别降低11.8%~14.7%、25.1%~33.7%和32.6%~43.9%；土壤生物有效态Zn含量分别降低14.1%~15.8%、59.7%~72.2%和43.2%~58.4%。     

活化赤泥的除氟性能

以成本低的铝工业废矿渣（赤泥）为原材料,通过高温煅烧和酸化处理对赤泥进行活化,制备了除氟吸附剂。研究了反应时间、投加量、初始氟浓度、溶液温度、共存阴离子和pH值对活化赤泥除氟效果的影响。结果表明,接触反应时间为18 h时,吸附接近平衡。活化赤泥对氟离子的吸附符合Lagergren二级吸附动力学方程。另外,初始浓度越高,吸附容量越大。与Freundlich相比,Langmuir吸附等温模型可以更好地描述氟离子的吸附特性,最大吸附量可达2.71 mg/g。SO24-、Cl-和NO3-存在时（〈1 000 mg/L）,对氟离子的吸附几乎没有影响,然而,HCO3-、PO34-和氟离子共存时,会对氟吸附造成不利影响。活化赤泥在pH值3.5～11.0时,具有较好的吸附稳定性。活化赤泥是一种吸附容量高、性能稳定的环境友好型除氟材料,具有应用潜力。     

Influence of arbuscular mycorrhizal fungi on the growth and nutrient status of bermudagrass grown in alkaline bauxite processing residue

A nursery experiment was conducted to evaluate the potential role of arbuscular mycorrhizal (AM) fungi in encouraging the vegetation cover on bauxite residue (red mud) sites. An alkali tolerant bermudagrass (Cynodon dactylon) adapted to local conditions were grown in red mud with different amendments with and without AM fungi to assess mycorrhizal effects on plant growth, mineral nutrition, metal uptake and neutralization of bauxite residue. Inoculation of AM fungi significantly increased the plant growth, nutrient uptake and reduced Fe, Al accumulation in plant tissue and also improved the soil physico-chemical and biochemical properties. Gypsum and sludge amended treatments inoculated with AM fungi had maximum biomass, nutrient uptake and reduced accumulation of metals. The neutralization of red mud was significant in presence of AM fungi than control. The experiment provided evidence for the potential use of bermudagrass in combination with AM fungi for ecological restoration of bauxite residue sites.     

Field evaluation of in situ remediation of a heavy metal contaminated soil using lime and red-mud

We evaluated the effectiveness of lime and red mud (by-product of aluminium manufacturing) to reduce metal availability to Festuca rubra and to allow re-vegetation on a highly contaminated brown-field site. Application of both lime and red mud (at 3 or 5%) increased soil pH and decreased metal availability. Festuca rubra failed to establish in the control plots, but grew to a near complete vegetative cover on the amended plots. The most effective treatment in decreasing grass metal concentrations in the first year was 5% red mud, but by year two all amendments were equally effective. In an additional pot experiment, P application in combination with red mud or lime decreased the Pb concentration, but not total uptake of Pb in Festuca rubra compared to red mud alone. The results show that both red mud and lime can be used to remediate a heavily contaminated acid soil to allow re-vegetation.     

Novel applications of red mud as coagulant, adsorbent and catalyst for environmentally benign processes

Red mud (RM) is a by-product of bauxite processing via the Bayer process. Its disposal remains an issue of great importance with significant environmental concerns. In the past decades, a lot of research has been done to utilize red mud for environmental-benign applications such as a building material additive and for metal recovery. In recent years, red mud has also been explored for gas cleaning and wastewater treatment. In this paper, we review varying novel applications of red mud as a coagulant and adsorbent for water and gas treatment as well as catalyst for some industrial processes. The environmental compatibility of red mud is discussed. Some directions of future research are also proposed. Red mud presents a promising application in water treatment for removal of toxic heavy metal and metalloid ions, inorganic anions such as nitrate, fluoride, and phosphate, as well as organics including dyes, phenolic compounds and bacteria. In addition, red mud can also be employed as catalysts for hydrogenation, hydrodechlorination and hydrocarbon oxidation. Moreover, leaching and eco-toxicological tests indicate that red mud does not present high toxicity to the environment before or after reuse.     

赤泥对污染土壤Pb、Zn化学形态和生物可给性的影响

通过土壤培养实验,研究添加赤泥对污染土壤中Pb、Zn化学形态和生物可给性的影响。结果表明,不同赤泥用量处理均可显著降低土壤中HOAc提取态Pb、Zn含量。当赤泥用量为5%时,培养1、2和3个月后,HOAc提取态Pb含量分别比对照下降62.5%、65.3%和73.5%;HOAc提取态Zn含量分别比对照下降56.7%、65.8%和67.4%。培养3个月后,只有1%赤泥用量处理显著降低了土壤中生物可给性Pb含量,而不同用量赤泥处理均显著降低了土壤中生物可给性Zn含量。研究表明赤泥是一种钝化污染土壤中Pb、Zn的潜力添加剂。     

赤泥投加控制河道底泥磷释放的影响因素

通过对不同赤泥投加比例下河道底泥磷释放作用的研究,发现底泥中铁铝磷与钙磷的比值(Fe/Al-P∶Ca-P)、铁磷比(Fe∶TP)及有机质含量(OM)是赤泥能否应用于河道底泥磷释放控制中的决定性因素。实验结果表明,只有当河道底泥中Fe/Al-P∶Ca-P小于0.88,Fe∶TP小于16.1,且有机质含量低于1.87%时,投加适量赤泥才能起到抑制河道底泥内源磷释放的作用;反之,赤泥的投加则有可能促进底泥内源磷的释放。在实际工程应用中,推荐赤泥与底泥的接触时间不低于7d,从而使赤泥的效能发挥到最佳状态。     

利用多年期赤泥和煤矸石制备烧结砖

以多年期赤泥和煤矸石为主要原料,分析了其化学成分和物性特征,通过设计不同的原料配比和烧结温度,探讨其最佳工艺条件以及各种参数指标,试图为赤泥的大宗化利用提供一种新的途径。实验结果表明最佳工艺条件为:多年期赤泥与煤矸石质量比为20∶80,成型压力为6 MPa,烧结温度为1 100℃左右保温2 h。烧结砖体"泛霜"现象基本消失,抗压强度为12.18 MPa、吸水率为21.6%,满足国家粉煤灰普通烧结砖GB5101-2003中的要求。     

New insights into the sorption mechanism of cadmium on red mud

Effectiveness and mechanism of cadmium (Cd) sorption on original, acidified and ball milling nano-particle red muds were investigated using batch sorption experiments, sequential extraction analysis and X-ray absorption near edge structure (XANES) spectroscopy. The maximum sorption capacity of Cd was 0.16, 0.19, and 0.21 mol/kg for the original, acidified, and nano-particle red muds at pH 6.5, respectively. Both acidification and ball-milling treatments significantly enhanced Cd sorption and facilitated transformation of Cd into less extractable fractions. The Cd L_III-edge XANES analysis indicated the formation of inner-sphere complexes of Cd similar to XCdOH (X represents surface groups on red mud) on the red mud surfaces although outer-sphere complexes of Cd were the primary species. This work shed light on the potential application of red mud to remediate Cd-contaminated soils and illustrated the promising tool of XANES spectroscopy for speciation of multicomponent systems of environmental relevance.