Treatment of Acid Mine Drainage Using Constructed Wetland in Tropical Environment： A Tanzania Case Report

The suitability of constructed wetland （CW） in were developed. The first experiment focused on zinc and treating acid mine drainage （AMD） was investigated. Two experiments nutrients removals. Four units of horizontal subsurface flow CWs were used, two cells planted with Phragmites mauritianus, one cell with Typha domingensis and one cell unplanted （control cell）. Artificial high concentrated AMD was used. It was mixed with domestic wastewater from the anaerobic waste stabilization pond （WSP） to ensure nutrient supply to the plants in the CW cells. The second experiment tested the tolerance of locally available macrophytes to the harsh acidic environment, while providing required condition for treatment of AMD. To accomplish this, another set of four CW cells planted with different types of macrophytes, namely Typha domingensis, Phragmites mauritianus, Vetiver grass and Papyrus, were used thereby subjecting them to varying acid concentration ofpH of 3.5, 3.0, 2.9 and 2.7. The study demonstrated adequate zinc removal from AMD which is related to sulphide precipitation. A CW cell planted with Typha domingensis showed higher zinc removal （80%-84%） compared to other cells. Different macrophytes showed different nutrient removal efficiency, but overall, for the type of wetland plants studied, phosphorous removal increased with decreasing pH while nitrogen removal behaved quite opposite. On the other hand, Typha domingensis, Phragmites mauritianus and Papyrus were observed to tolerate high acidity as low pH as 2.7 and therefore are suitable macrophytes for AMD treatment with CW.

Removal of Copper Ions from Acid Mine Drainage Wastewater Using Ion Exchange Technique: Factorial Design Analysis

A factorial experimental design method was used to examine the “Cu2+” removal from acid mine drainage wastewater by ion exchange technique. Ion Exchange technique is preferred because of reduced sludge generation compared to conventional treatment techniques and better decontamination efficiency from highly diluted solutions. Factorial design of experiments is employed to study the effect of four factors pH (3, 5, and 6), flow rate (5, 10, 15 L/hr), resin bed height (20, 40 and 60 cm) and initial concentration of the metal (100, 150 and 200 mgl-1) at three levels. The efficiency of metal removal was determined after 100 min of treatment. Main effects and interaction effects of the four factors were analyzed using statistical techniques. A regression model was recommended and it was found to fit the experimental data very well. The results were analyzed statistically using the Student’s t-test, analysis of variance, F-test and lack of fit to define most important process variables affecting the percentage “Cu2+” removal. In this study , pH was thus found to be the most important variable.

Effect of hydraulic retention time and pH on oxidation of ferrous iron in simulated ferruginous acid mine drainage treatment with inoculation of iron-oxidizing bacteria

The effect of hydraulic retention time (HRT) and pH on the biooxidation of ferrous iron during simulated acid mine drainage (AMD) treatment was investigated.The simulated AMD was highly acidic (pH 2.5), rich in iron (about 1700 mg/L) and copper (about 200 mg/L), and contained high concentrations of sulfate (about 4700 mg/L).The biooxidation of ferrous iron was studied in a laboratory-scale upflow packed bed bioreactor (PBR).The HRT was shortened stepwise from 40 h to 20 h, 13 h, and 8 h under the acidic environment at a pH value of 2.2.Then, the influent pH value was changed from 2.2 to 1.2 at a constant suitable HRT.Physiochemical and microbial community structure analyses were performed on water samples and stuffing collected from the bioreactor under different conditions.The results indicate that the efficiency of ferrous iron oxidation gradually decreased with the decrease of HRT, and when the HRT exceeded 13 h, ferrous iron in AMD was almost completely oxidized.In addition, the best efficiency of ferrous iron oxidation was achieved at the influent pH value of 1.8.Microbial community structure analyses show that Leptospirillum is the predominant genus attached in the bioreactor, and low influent pH values are suitable for the growth of Leptospirillum.

Environmental Assessment of Acid Mine Drainage Pollution on Surface Water Bodies around Ngwenya Mine, Swaziland

Twenty-three water samples and three “yellow boy” samples were obtained from different water bodies located at the foot of the Ngwenya Mountain on top of which the old Ngwenya Iron Ore Mine is located. The samples were analysed for pH, electrical conductivity (EC), redox potential (ORP) and temperature (T). The dominant Fe species was determined using a UV-VIS spectrophotometer. Selected anions namely: halogens (F-, Br-, Cl-), the nutrients (NO2-,NO3-,PO43-) and the best indicator for AMD pollution (SO42-) were analysed using Ion Chromatography (IC) while the selected heavy metals, namely: Cr, Mn, Fe, Ni, Co, Cu, Zn, Pb and Cd were analysed using Flame Atomic Absorption Spectrometry (FAAS). The physico-chemical parameters ranges obtained were pH (6.32 - 8.63), EC (11.00 - 585.33 μS/cm), ORP (-93.67 - 79.33 mV) and T (7.60°C - 18.57°C). The levels of the Fe species (ppm) in the water samples were Fe2+ (0.56 - 3.17) and Fe3+ (0.00 - 0.73). Measured mean anion ranges in ppm were F- (0.00 - 0.15), Cl- (1.5 - 11.19),

An effective way to treat the iron-rich acid mine drainage from coal mining in Guizhou’s mountainous areas

Acid Mine Drainage(AMD)from coal mining is a serious environmental issue which affects water quality,ecology,and the overall landscape of the basin.A large number of coal mine tailings in the mountainous regions of Guizhou Province,China were unattended and iron-rich AMD was directly discharged to the rivers.This discharge leaves the river―yellow‖and heavily polluted.This study tries to find an efficient and economical method for treating iron-rich AMD.We sampled AMD water in two sites:Yangliujie town of Duyun city(hereafter,called Yangliujie),and Xinglong Coal Mine,Duliu town of Guiding county(hereafter,called Xinglong).We performed iron removal laboratory experiment with Cement-Bentonite Agent(CBA,80%cement and 20%bentonite)in 500 mL AMD water from Yangliujie,scale-up experiment in 15 L AMD water from both Yangliujie and Xinglong,and engineering application in Xinglong respectively.Laboratory experiment results showed the iron removal rate can reach 99.8%and the removal rate depends on the CBA dosage and the treatment time.In the scale-up experiment,we found that Fe concentration could be reduced from 587.0 to 0.2 mg/L when adding 20 g/L CBA to the AMD water and aerating for 3 hours.As sampled water in Xinglong has a very high Fe concentration(Fe 1019.8 mg/L)and the concentration varies with seasons,it is not economical to add the CBA directly to the AMD water.Considering the abundant and cheap limestone resources in Guizhou,we used a twostep treatment method,first we added CaCO3 to raise the pH,and then we took the supernatant liquor and added CBA to the liquor.It was shown that 15 g/L of CBA was a good dosage for iron removal with Fe concentration being reduced from 1019.8 to 0.3 mg/L when CaCO3 was used to raise the pH.The best treatment realized over 99.9%iron removal,99.2%NH3-N removal,98.9%CODMn removal,and heavy metals in the treated water were reduced to under the limit stipulated in the―Environmental Quality Standards of Surface Water in China‖.Thus in the engineering application,we used this two-step treatment method.After the treatment,the pH of the iron-rich AMD(pH 2.86,Fe 2624.6 mg/L)increased to 8.53,the concentration of Fe was reduced to 59.5 mg/L,NH3-N decreased from 16.15 to less than 0.05 mg/L,CODMn decreased from 323.33 to 24.57 mg/L,heavy metals except Fe and Mn were reduced to under the limit of surface water.In conclusion,the use of CBA can effectively remove Fe and other heavy metals from the iron-rich AMD and adjust the pH value to the range of a natural water body.

The Dynamic Experiment on Treating Acid Mine Drainage with Iron Scrap and Sulfate Reducing Bacteria Using Biomass Materials as Carbon Source

The study is aimed at the problem of high content of Cr^(6+),Cr^(3+)and SO_(4)^(2-)is high and low pH value in acid mine drainage(AMD).Moreover,treatment of AMD by sulfate reducing bacteria(SRB)requires the addition of carbon source,while the treating effectiveness is not good enough on its own.The sugarcane slag,the corn cob and the sunflower straw were selected as the SRB carbon source cooperating with iron scrap to construct the dynamic columns 1,2 and 3.The mechanism of removing Cr^(6+),Cr^(3+),SO_(4)^(2-)and H+and the regularity of sustained release of carbon source and TFe release was studied in AMD.The removal efficiency of heavy metal ions,the ability of sustained release of carbon source,and the ability of adjusting acid by the three dynamic columns were compared.The result shows that the average removal rates of Cr^(6+),Cr^(3+)and SO_(4)^(2-)in effluent of dynamic column 1,filled by sugarcane slag,iron scrap and SRB,were 96.9%,67.1%and 54.3%.The average release of TFe and chemical oxygen demand(COD)were 4.4 and 287.3 mg/L.Its average pH was 6.98.Compared with the performance of dynamic columns 1,2 and 3,dynamic column 1 performed best in removing Cr^(6+),Cr^(3+)and SO_(4)^(2-)from AMD and controlling the release of COD and TFe,adjusting the pH of the solution.The study is of significance in treatment of AMD by taking for biomass materials as SRB carbon source in cooperation with iron scrap.

Influence of acid leaching and calcination on iron removal of coal kaolin

Calcination and acid leaching of coal kaolin were studied to determine an effective and economical preparation method of calcined kaolin. Thermogravimetric-differential thermal analysis （TG-DTA） and X-ray diffraction （XRD） demonstrated that 900＆#176;C was the suitable temperature for the calcination. Leaching tests showed that hydrochloric acid was more effective for iron dissolution from raw coal kaolin （RCK）, whereas oxalic acid was more effective on iron dissolution from calcined coal kaolin （CCK）. The iron dissolution from CCK was 28.78wt%, which is far less effective than the 54.86wt% of RCK under their respective optimal conditions. Through analysis by using M？ssbauer spectroscopy, it is detected that nearly all of the structural ferrous ions in RCK were removed by hydrochloric acid. However, iron sites in CCK changed slightly by oxalic acid leaching because nearly all ferrous ions were transformed into ferric species after firing at 900＆#176;C. It can be concluded that it is difficult to remove the structural ferric ions and ferric oxides evolved from the structural ferrous ions. Thus, iron removal by acids should be conducted prior to calcination.

Benzohydroxamic acid to improve iron removal from potash feldspar ores

The technological mineralogy of the potash feldspar was investigated and a new collector named Yb105 was adopted to remove iron from potash feldspar ores.The technological mineralogy results indicate that the main components of the ore were feldspar,sericite,quartz and kaolinite,and iron mainly existed in limonite and hematite,most of which can be removed by beneficiation.The results show the benzohydroxamic acid can not only increase the recovery of iron and reduce the consumption of oleic acid collector,but also enhance the collecting performance of oleic acid at low temperature,which can realize the flotation of the ores at a low temperature and play an important role in saving energy to some extent.Compared with oleic oil,the benzohydroxamic acid had a great advantage in removing iron from potash feldspar,a potash feldspar concentrate with Fe grade of 0.23%,K2O grade of 12.59%and Na2O grade of 0.26%was obtained by flotation with Yb105 as collector,and the yield of the concentrate was 82.55%.

Isolation and characterization of acidophilic bacterium from Gaofeng Mine in China

An acidophilic,chemolithotrophic and ferrous oxidizing bacterium strain GF was isolated from the acid mine drainage (AMD) of Gaofeng Mine,Guangxi Province,China using 9K enrichment medium,and then purified on solid ferrous-agarose medium.The physiological experiments show that it can use ferrous or sulfur as sole energy and a low level (0.1%,w/v) of peptone can accelerate the growth of the isolated strain.The optimum pH and temperature for growth are 2.0 and 30 ℃,respectively.The isolated strain shares 99.64% identities of 16S rRNA gene with the type strain Acidthiobacillus ferrooxidans ATCC 23270 and 100% identities of iro gene (CDS) with A.ferrooxidans strain Fe-1.These results show that the strain can be considered as Acidthiobacillus ferrooxidans.Because of the high activity of oxidizing ferrous and sulfide mineral,strain GF was used in bioleaching of marmatite.The Zn concentration is 0.273 g/L under the steriled control and 7.30 g/L with adapted GF strain incubated after 29 d in leaching marmatite.The isolated strain GF can be used to leach marmatite in industry application.

Bioremediation Process and Bioremoval Mechanism of Heavy Metal Ions in Acidic Mine Drainage

Acidic mine drainage（AMD） containing acidity and a broad range of heavy metal ions is classified as hazardous, and must be properly treated. The removal mechanism of heavy metal ions in acidic mine drainage containing Cu^2＋, Fe^2＋, and Zn^2＋ with biological method was studied here. Using 20 mmol/L ethanol as carbon source, Desulfovibrio marrakechensis, one of sulfate reducing bacteria（SRB） species, grew best at 35℃ and pH=6.72 with concentrations of 10, 55 and 32 mg/L for Cu^2＋, Fe^2＋ and Zn^2＋, respectively. The removal efficiency for each ion mentioned above was 99.99%, 87.64% and 99.88%, respectively. The mineralogy and surface chemistry of precipitates were studied by means of energy dispersive spectrometer（EDS）, X-ray photoelectron spectroscopy（XPS）, X-ray diffraction（XRD） combined with control tests. The experimental results demonstrate that the removal mechanism of heavy metal ions by Desulfovibrio marrakechensis is comprehensive function of chemical precipitation, adsorption and bioprecipitation. The biogenic iron sulfide solid was characterized as greigite（Fe3S4）, while the zinc sulfide solid was characterized as sphalerite（ZnS）.

除铁减酸反应池处理酸性矿山废水的效果研究

通过对除铁减酸反应池(RIAUM)处理酸性矿山废水(AMD)的效果进行持续监测与系统采样分析,查明了RIAUM处理系统中AMD的pH、酸度、总铁以及亚铁等理化指标的变化规律,评估了RIAUM处理系统对不同理化指标的净化效果,探讨了RIAUM各单元的潜在除铁减酸机制。结果表明:RIAUM处理系统运行效果稳定,具有良好的除铁减酸能力,Fe平均去除率在94.00%以上,出水Fe浓度满足《煤炭工业污染物排放标准(GB 20426—2006)》的限值要求;酸度平均去除率为70.29%;此外,RIAUM对Mn、Pb、Cr、Cd、SO_(4)^(2-)均具有一定的去除效果,去除率分别为37.34%、61.65%、86.82%、39.42%、28.56%。RIAUM的潜在除铁减酸机制主要为:氧化沉淀反应单元通过化学氧化沉淀作用和帷幕吸附与过滤作用除铁;微生物反应单元可能存在“二元”Fe净化机制,即在表层水体中,除化学氧化作用外,微生物如铁氧化细菌介导催化了Fe(Ⅱ)的快速氧化沉淀,而在底层水体中则可能依靠硫酸盐还原菌等厌氧细菌介导的SO_(4)^(2-)的还原产生的S2-与水体中的Fe反应生成低溶解度的铁硫化物沉淀,但该作用机制还有待进一步研究证实;碱中和反应单元中,碳酸盐岩溶解能够中和酸度,提升水体pH值。除铁减酸反应池的成功应用将为酸性矿山废水的治理提供重要的理论指导和潜在的技术支撑。

关闭煤矿矿井水中“双源”铁污染的电化学机理实验模拟

关闭煤矿矿井水多呈现高铁特征,闭坑淹井后残留铁质器件易锈蚀,与含铁矿物形成矿井水“双源”铁污染体系,在闭坑后不同时期贡献铁的释放,形成地下水环境风险。为明确关闭煤矿矿井水中双源铁释放过程与反应机理,刻画铁污染双源释放方式,量化释放速率比,基于电化学模拟原理,以黄铁矿和矿用锚杆为模拟“双源”,制备成工作电极,利用循环伏安法和极化法等电化学方法以及X射线光电子能谱材料表面表征技术,对煤矿关闭初期双源共存下在酸性矿井水环境中氧化还原反应过程与铁释放机制进行了模拟研究。结果表明,溶解氧含量是影响黄铁矿和锚杆在酸性矿井水中发生氧化还原反应的重要抑制因素。黄铁矿与锚杆的氧化机制不同,黄铁矿在氧化过程中表面出现钝化效应,2种材料的最终氧化产物均为Fe^(3+)和SO_(4)^(2-)黄铁矿主要通过矿物表面的Fe^(2+)发生氧化反应释铁,锚杆主要通过材料表面铁及其氧化产物与溶液中酸性物质的反应释铁,且铁氧化物较单质铁优先反应。在模拟富氧(DO=7.0 mg/L)酸性矿井水中,黄铁矿和锚杆的年腐蚀速率分别达到8.3636 mm/a和7.8314 mm/a,估算年释铁速率分别达到1.2240 g/a和3.9395 g/a。在模拟井下低氧(DO=3.5 mg/L)酸性矿井水中,黄铁矿和锚杆的年腐蚀速率分别达到0.7324 mm/a和0.3642 mm/a,估算年释铁速率分别达到0.1072 g/a和0.1832 g/a。综合电化学参数与静态释铁实验表明,在溶解氧充足或缺乏的条件下,总体释铁速率比均为双源>锚杆>黄铁矿。

废旧电池回收过程中磷酸铁渣的提纯

为实现磷酸铁渣高附加值资源回收利用,采用盐酸浸出渣中铁、铁粉置换除铜、水解-化学沉淀法去除浸出液中钛、铝。结果表明,盐酸浓度25%、液固比6 mL/g、浸出温度60℃、浸出时间60 min时,磷酸铁渣中铁浸出率达98.7%;控制溶液初始pH=0.6,铁粉添加量为浸出液中铁物质的量0.55倍、反应温度60℃、反应时间35 min时,铜去除率达96.2%,钛去除率达83.6%;水解-化学沉淀法除钛、铝的过程中,氟化钠与铝物质的量比8∶1、反应pH=1.9、反应温度40℃、反应时间30 min时,钛去除率达97.6%,铝去除率达99.3%,浸出液中杂质元素含量满足后续电池级磷酸铁的制备要求。

红土镍矿硝酸加压浸出渣制备电池级磷酸铁

近年来,在我国“碳达峰”和“碳中和”目标的引领下,新能源行业发展迅速,新能源汽车的推广与使用促进了锂离子电池行业的蓬勃发展。作为三元锂电池的关键原材料,镍的需求量不断增加。但由于硫化镍矿日益枯竭,红土镍矿逐渐成为了主要的提镍原料,在镍产量中占比超过70%。褐铁型红土镍矿在红土镍矿中占比超过60%,经硝酸加压浸出(NAPL)提取镍钴后产生的浸出渣中含有丰富的有价金属资源(铁含量>60%),浸出渣的综合利用对资源回收和环境保护具有重要意义。以褐铁型红土镍矿硝酸加压浸出渣为原料,在磷酸单一介质中制备电池级磷酸铁材料。以磷酸为介质,通过预浸、溶解实现浸出渣中铁的高效提取。预浸时磷酸溶液浓度较低,可以使含铁相初步转型为FePO_(4)·2H_(2)O,同时除去浸出渣中Cr、Mg、Al等杂质元素。然后采用高浓度磷酸溶液溶解处理预浸渣,实现Fe的完全溶解。最后稀释调节pH值直接沉淀制备磷酸铁,得到FePO_(4)·2H_(2)O产品,该产品不含杂质元素Mg、Si,Cr、Al的含量为0.019%、0.016%。通过XRD、SEM、EDS等技术手段对预浸渣和磷酸铁产品的物相组成和微观形貌进行了研究,明确了预浸过程可实现铁由Fe_(2)O_(3)向FePO_(4)·2H_(2)O的转变,最终产品的晶体结构与标准磷酸铁相匹配。由磷酸铁合成的磷酸铁锂材料也表现出优异的电化学性能。该研究有望实现对褐铁型红土镍矿硝酸加压浸出渣中宏量组元铁的高值化利用,从而优化磷酸铁制备工艺。

某酸性矿山废水综合治理试验研究

针对某有色金属矿山周边酸性矿山废水存在环境污染隐患问题,进行了除铁、硫化收铜、中和处理试验研究。结果表明:该酸性矿山废水采用混合除铁收铜—中和处理后,污染物达到GB 8979—1996《污水综合排放标准》一级标准要求,产生的中和渣浸出毒性能够满足一般工业固体废物要求,铜渣铜品位可达到35%以上,铜综合回收率可达93.9%。

偏钛酸中亚铁离子脱出的研究

硫酸法生产钛白粉过程中,偏钛酸的含铁量严重影响钛白粉的白度。作者利用硫酸亚铁与不同配位剂进行配位,探究适合的配位剂。再利用配位剂与偏钛酸中亚铁离子进行配位,通过水洗过滤的方式将亚铁配合物与偏钛酸进行分离,从而获得低含铁量的偏钛酸,提高成品钛白粉的品质。实验结果表明邻菲啰啉溶液与偏钛酸反应时,邻菲啰啉量大除铁效果好。

硫铁矿烧渣制备电池级磷酸铁工艺研究

硫铁矿烧渣是硫铁矿生产硫酸过程中产生的固体废弃物,其大量堆积带来了严重的生态环境问题。经适当处理的硫铁矿烧渣中较高价的铁含量高,若能提取利用,不仅可以解决生态环境问题,还可以带来一定的经济效益。本文通过添加固体还原剂高温焙烧,成功将硫铁矿烧渣中较高价的铁(Fe 2 O 3)还原为较低价的铁(Fe 3 O 4)。通过单因素试验,得到了较优的还原焙烧条件:在850~900℃下焙烧45~60 min,还原剂化学计量比为1.4~1.7;较优的酸浸条件:硫酸质量分数为30%~40%,硫酸化学计量比为1.2~1.4,浸取时间在30 min以上。在上述条件下,铁的浸出率高达98%。对酸浸液进行除杂处理,利用除杂后的硫酸亚铁净化液制备了磷酸铁产品,经检测,产品质量达到了HG/T 4701-2021《电池用磷酸铁》的技术指标要求。研究成果为硫铁矿烧渣的高值利用提供了一条新途径。

A new route of ferric ions rejection in a synthetic nickel leach solution

A new route of impurity rejection to remove ferric iron from a synthetic nickel leach solution was introduced, which simulated the chemical composition of a typical acid leach solution of nickel laterites under atmospheric pressure. The synthetic solution underwent a stepwise neutralization process, with each step adopting different pH value-temperature combinations. In a conventional nickel atmospheric leach （AL） process, the nickel loss could be as high as 10wt%, which was a longstanding issue and prevented this process from commercialization. The new impurity rejection route is the first step towards resolving this issue. The results show that, the best neutralization performance is achieved at the nickel loss of 3.4wt% in the neutralization scheme that employs ethylenediaminetetraacetic acid as a nickel stabilizer （pH： 1.3-3.5; temperature： 95-70℃）

矿山酸性水中铝相次生矿物及环境学意义的研究进展

酸性矿山排水(AMD)是硫化矿床矿山环境污染防治的难点,因而持续受到国内外学者的关注。众多的学者对矿区AMD中次生矿物进行了研究。为深入了解AMD中次生矿物的形成和演化,为AMD污染防治提供科学依据,笔者对前人不同环境下AMD中的次生矿物类型、次生矿物形成顺序,以及铝相次生矿物的形成、特征、环境危害及意义进行了简要综述。目前与AMD有关的主要次生矿物存在3种类型,即铁相次生矿物、铝相次生矿物和其他相次生矿物,AMD中的pH、Eh和温度对于次生矿物的形成具有控制性的作用。铁、铝相次生矿物具有吸附金属能力,这一性质有助于在一定程度上实现河流的自净化作用。由于AMD形成条件高,矿物相不稳定,目前有关AMD中铝相次生矿物及“酸性白水”的研究成果有限。因此,加强铝相次生矿物以及“酸性白水”的研究,可以更好地解析蒿坪河流域石煤矿区河流酸性磺水-酸性白水的形成演化机制,以及铝相次生矿物吸附重金属的地球化学过程。