Humic Acid and Iron Chelation Modified Anode Improves the Electrochemical Performance of Marine Sediment Microbial Fuel Cell

Marine sediment microbial fuel cell(MSMFCs)can be utilized as a long lasting power source to drive small instruments to work for long time on ocean floor and its higher power has a significant meaning for practical application.Anode modification can greatly improve the performance of MSMFCs.Herein,humic acid(HA)and humic acid-iron ion complex(HA-Fe)were used to modify the anode for constructing a better MSMFCs.The results indicated that HA-Fe modified anode,better than HA modification,significantly improved the MSMFCs cell power output.The maximum power density of HA-Fe modified MSMFCs is 165.3 mW m−2,which are 6.5-folds of blank MSMFCs.The number of microorganisms on anode,redox activity,and relative kinetic activity were 1.8-,6.1-,and 13.1-folds of blank MSMFCs,respectively.The MSMFCs improvement would be attributed to the electron transfer media of HA and the valence conversion of Fe ions.A synergistic interaction between the naturally occurring HA and Fe ions on the anodic surface in marine sediments would make the modified anodes have‘renewable’characteristics,which is beneficial for the MSMFCs to maintain its long-term higher power.

Effects of iron and humic acid on competition between Microcystis aeruginosa and Scenedesmus obliquus revealed by HPLC analysis of pigments

Iron is a vital micronutrient for growth of bloom-forming Microcystis aeruginosa and competition with other algae,and its availability is affected by humic acid.The effect of iron and humic acid on growth and competition between M.aeruginosa and Scenedesmus obliquus was assessed.The results showed the growth of M.aeruginosa and S.obliquus in mono-cultures was inhibited by humic acid at low iron concentrations(0.01 mg/L);the maximum inhibition ratios were 67.84%and 38.31%,respectively.The inhibition of humic acid on the two species was significantly alleviated when iron concentrations were 1.00 mg/L,with the maximum inhibition rate reduced to 5.82%for M.aeruginosa and to 23.06%for S.obliquus.S.obliquus was the dominant species in mixed cultures,and the mutual inhibition between M.aeruginosa and S.obliquus at low iron concentration was greater than that at high iron concentration.The inhibition of S.obliquus on M.aeruginosa was reduced at low iron concentrations;it increased at high iron concentrations,as concentrations of humic acid rose.

Dissimilatory iron reduction contributes to anaerobic mineralization of sediment in a shallow transboundary lake

Dissimilatory iron reduction(DIR)coupled with carbon cycling is increasingly being recognized as an influential process in freshwater wetland soils and sediments.The role of DIR in organic matter(OM)mineralization,however,is still largely unknown in lake sediment environments.In this study,we clarified rates and pathways of OM mineralization in two shallow lakes with seasonal hydrological connectivity and different eutrophic situations.We found that in comparison with the domination of DIR(55%)for OM mineralization in Lake Xiaoxingkai,the contribution of methanogenesis was much higher(68%)in its connected lake(Lake Xingkai).The differences in rates and pathways of sediment OM mineralization between the two lakes were attributed to higher concentrations of carbonate associated iron oxides(Fecarb)in Lake Xiaoxingkai compared to Lake Xingkai(P=0.002),due to better deposition mixing,more contributions of terrigenous detrital materials,and higher OM content in Lake Xiaoxingkai.Results of structural equation modeling showed that Fecarb and total iron content(TFe)regulated 25%of DIR in Lake Xiaoxingkai and 76%in Lake Xingkai,accompanied by a negative effect of TFe on methanogenesis in Lake Xingkai.The relative abundance and diversity of Fe-reducing bacteria were significantly different between the two lakes,and showed a weak effect on sediment OM mineralization.Our findings emphasize the role of iron minerals and geochemical characterizations in regulating rates and pathways of OM mineralization,and deepen the understanding of carbon cycling in lake sediments.

Humic acid and metal ions accelerating the dechlorination of 4-chlorobiphenyl by nanoscale zero-valent iron

Transformation of polychlorinated biphenyls （PCBs） by zero-valent iron represents one of the latest innovative technologies for environmental remediation. The dechlorination of 4-chlorobiphenyl （4-C1BP） by nanoscale zero-valent iron （NZVI） in the presence of humic acid or metal ions was investigated. The results showed that the dechlorination of 4-C1BP by NZVI increased with decreased solution pH. When the initial pH value was 4.0, 5.5, 6.8, and 9.0, the de.chlorination efficiencies of 4-CIBP after 48 hr were 53.8%, 47.8%, 35.7%, and 35.6%, respectively. The presence of humic acid inhibited the reduction of 4-CIBP in the first 4 hi＇, and then significantly accelerated the dechlorination by reaching 86.3% in 48 hr. Divalent metal ions, Co2＋, Cu2＋, and Ni2＋, were reduced and formed bimetals with NZVI, thereby enhanced the dechlorination of 4-CIBP. The dechlorination percentages of 4-CIBP in the presence of 0.1 mmol/L Co2~, Cuz~ and Niz~ were 66.1%, 66.0% and 64.6% in 48 hr, and then increased to 67.9%, 71.3% and 73.5%, after 96 hr respectively. The dechlorination kinetics of 4-C1BP by the NZVI in all cases followed pseudo-first order model. The results provide a basis for better understanding of the dechlorination mechanisms of PCBs in real environment.

Effect of environmental factors on the complexation of iron and humic acid

A method of size exclusion chromatography coupled with ultraviolet spectrophotometry and off-line graphite furnace atomic absorption spectrometry was developed to assess the complexation properties of iron（Fe） and humic acid（HA） in a water environment. The factors affecting the complexation of Fe and HA, such as ionic strength, pH, temperature and UV radiation, were investigated. The Fe–HA complex residence time was also studied. Experimental results showed that pH could influence the deprotonation of HA and hydrolysis of Fe, and thus affected the complexation of Fe and HA. The complexation was greatly disrupted by the presence of NaCl. Temperature had some influence on the complexation. The yield of Fe–HA complexes showed a small decrease at high levels of UV radiation, but the effect of UV radiation on Fe–HA complex formation at natural levels could be neglected. It took about 10 hr for the complexation to reach equilibrium, and the Fe–HA complex residence time was about 20 hr.Complexation of Fe and HA reached a maximum level under the conditions of pH 6, very low ionic strength, in the dark and at a water temperature of about 25°C, for 10 hr. It was suggested that the Fe–HA complex could form mainly in freshwater bodies and reach high levels in the warm season with mild sunlight radiation. With changing environmental parameters, such as at lower temperature in winter or higher pH and ionic strength in an estuary, the concentration of the Fe–HA complex would decrease.

Underestimation of phosphorus fraction change in the supernatant after phosphorus adsorption onto iron oxides and iron oxide–natural organic matter complexes

The phosphorus（P） fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid（HA） complexes were analyzed using the ultrafiltration method in this study.With an initial P concentration of 20 mg/L（I =0.01 mol/L and pH = 7）,it was shown that the colloid（1 kDa-0.45 μm） component of P accounted for 10.6%,11.6%,6.5%,and 4.0%of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite（FH）,goethite（GE）,ferrihydrite-humic acid complex（FH-HA）,goethite-humic acid complex（GE-HA）,respectively.The 〈1 kDa component of P was still the predominant fraction in the supernatant,and underestimated colloidal P accounted for 2.2%,55.1%,45.5%,and 38.7%of P adsorption onto the solid surface of FH,FH-HA,GE and GE-HA,respectively.Thus,the colloid P could not be neglected.Notably,it could be interpreted that Fe3＋ hydrolysis from the adsorbents followed by the formation of colloidal hydrous ferric oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant.And colloidal adsorbent particles co-existing in the supernatant were another important reason for it.Additionally,dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant.Ultimately,we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P,even when considering other contaminants such as organic pollutants,heavy metal ions,and arsenate at the sediment/soil-water interface in the real environment.

Immobilized iron functionalised imidazolium-based ionic liquid:Solvent-free and recoverable heterogeneous catalytic application for the synthesis of amines under green conditions

We reported solvent-free and recoverable heterogeneous iron functionalised imidazolium-based ionic liquid for the reduction of nitroarene derivatives in the presence of formic acid under greener conditions.Additionally,the experimental result shows that the iron complex could be an extremely resourceful,high rate and reusable catalyst for a different nitroarene substrate.

Effect of modified humic acid binder on pelletisation of specularite concentrates

A modified humic acid(MHA) binder was tested as a substitute for bentonite to prepare qualified specularite pellets. The results show that there is stronger chemisorption between organic functional groups in MHA binder molecular and specularite particles, improving the green pellet strength. MHA binder has obvious effect on the strength and microstructure of preheated pellets due to the thermal decomposition of organic matters in MHA binder. Appropriately increasing preheating temperature or time can eliminate the adverse impact of organic matters on the preheated pellet strength. Compared with the bentonite pellets, the roasted pellets with MHA binder have a more compact microstructure, and the recrystallization of the Fe2O3 crystal grains is better.Consequently, under optimal conditions, 0.75%(mass fraction) MHA binder pellets have equal or better pellet strengths and contain1.06% more total iron than 2 % bentonite pellets. The testing results indicate that MHA binder is a promising and effective alternative to bentonite for the specularite pellets.

纳米Fe_(3)O_(4)/生物炭促进红壤性水稻土中六氯苯厌氧脱氯作用研究

为明确磁铁矿(Fe_(3)O_(4))与生物炭对厌氧土壤中六氯苯(HCB)还原脱氯降解的影响及其机理,首先制备并表征了纳米Fe_(3)O_(4)、生物炭及纳米Fe_(3)O_(4)/生物炭复合材料,采用红壤性水稻土的泥浆进行厌氧培养试验,分析反应体系的pH、Eh、吸附态和溶解态Fe(Ⅱ)与HCB脱氯降解过程之间的内在关系。结果发现,灭菌对照处理的HCB脱氯降解作用很弱,表明HCB还原脱氯主要在微生物的作用下进行;添加生物炭可通过降低土壤的酸性、增强反应体系的还原性且促进生成吸附态Fe(Ⅱ)而加速HCB还原脱氯降解;纳米Fe_(3)O_(4)促进HCB还原脱氯的效果较生物炭更强,主要归因于添加纳米Fe_(3)O_(4)使反应体系中生成更多的吸附态Fe(Ⅱ);纳米Fe_(3)O_(4)/生物炭复合材料促进HCB还原脱氯的效果较纳米Fe_(3)O_(4)更强,是因为Fe_(3)O_(4)/生物炭复合材料的比表面积更大且纳米Fe_(3)O_(4)的分散性更好,更有利于反应体系中的电子传递过程。因此,与纳米Fe_(3)O_(4)和生物炭相比,纳米Fe_(3)O_(4)/生物炭复合材料是一种更加理想的HCB污染土壤的修复剂。

有机酸-硫化零价铁处理高浓度含铬废液及铬铁资源化的研究

针对含铬废液净化污泥杂质含量高、铬含量低导致铬回收难的问题,以有机酸-硫化零价铁为铬废液净化剂,在高效去除废液中铬的同时,可净化污泥并直接制备铬铁合金。通过考察零价铁硫化程度、初始废液pH值、不同有机酸摩尔比、硫化零价铁用量等影响因素对废液铬净化与污泥铬富集的影响,探索铬污泥直接制备铬铁合金工艺。研究显示,采用有机酸-硫化零价铁协同处理后,废液总铬质量浓度可由5 324.1 mg/L降低至4.30 mg/L,与未改性零价铁技术相比,铬净化去除率由65.45%提高至99.92%。净化污泥铬铁元素平均质量分数大于46%,在1 500℃,氩气保护气氛下,添加质量分数为30%碳粉即可成功制备铬铁合金。铬铁合金产物中铬铁元素分布均匀,杂质含量较少。XRD分析显示,硫化零价铁的掺入质量增大可降低合金产品中杂相的生成。研究方法为冶金、化工等行业含铬废液的高效净化及资源化处理提供了一条新路径。

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。

不同铁矿物对酱香型白酒封窖泥厌氧消化的影响

通过向废弃窖泥厌氧消化系统中分别添加强氧化性的水铁矿和弱氧化性但有导电性的磁铁矿,考察Fe(Ⅱ)、有机物、微生物群落结构等的变化,探究不同类型Fe(Ⅲ)矿物对窖泥厌氧消化的影响。结果表明,水铁矿组富集铁还原菌,Fe(Ⅱ)含量第12天迅速增加至900 mg/L,表明水铁矿发生了异化铁还原。磁铁矿组与对照组中Fe(Ⅱ)含量几乎一致,说明磁铁矿没有发生异化铁还原。水铁矿组和磁铁矿组中COD去除量分别比空白组增加了16.1%和4.9%,表明水铁矿和磁铁矿均促进了有机物的去除。磁铁矿组富集了Geobacter和Methanosarcina,促进了直接种间电子传递(DIET),增加了23.4%的甲烷产量,而水铁矿抑制甲烷化,降低了32.2%的甲烷产量。

黄腐酸螯合锌、铁叶面肥的制备及其施肥效果研究

以生化黄腐酸(BFA)为原料,通过超声活化法制备黄腐酸叶面肥(ABFA),以ABFA为螯合剂,硫酸亚铁(FeSO_(4))为铁源、硫酸锌(ZnSO_(4))为锌源,制备黄腐酸螯合铁叶面肥(ABFA-Fe)、黄腐酸螯合锌叶面肥(ABFA-Zn).在单因素实验基础上,以螯合率为指标,采用正交实验优化ABFA-Fe、ABFA-Zn最佳制备条件.通过UV-Vis、FT-IR、XPS、XRD和SEM对三种叶面肥的结构与形貌进行了表征.结果表明,ABFA-Fe的最佳制备条件为:pH=5、反应温度50℃、m(ABFA)∶m(FeSO_(4))=1∶2、反应时间60 min,螯合率59.93%;ABFA-Zn的最佳制备条件为:pH=7、反应温度30℃、m(ABFA)∶m(ZnSO_(4))=1∶2、反应时间120 min,螯合率85.93%.种植实验结果表明,ABFA-Fe、ABFA-Zn可有效提高叶片叶绿素含量,促进小油菜生长.

沉积物异化铁还原耦合植酸去磷酸化

研究沉积物中微生物驱动的异化铁还原与有机磷降解转化的耦合作用,对深入阐明水体富营养化发生机制、控制环境磷污染和应对潜在的全球性磷危机具有重要的现实意义。该研究以沉积物异化铁还原与有机磷降解转化耦合的环境效应为切入点,探究了异化铁还原促进植酸有机磷去磷酸化的可行性。首先通过对武汉东湖自然沉积物中有机磷与亚铁含量的监测,以及两者之间的相关性分析,发现在以有机质降解为驱动力的早期成岩过程中,三价铁逐渐被还原为亚铁,同时伴随着有机磷含量的降低,揭示沉积物中铁的异化还原可能促进有机磷的降解转化;接着利用富集的沉积物内源微生物群落在实验室构建“异化铁还原微生物群落+水铁矿+植酸”微宇宙模拟系统,开展了铁还原微生物群落驱动异化铁还原对植酸有机磷降解转化作用的研究,进一步证实铁的异化还原能促进植酸有机磷的去磷酸化并生成PO_(4)^(3-),很可能是诱导水体富营养化的潜在新机制。

钕铁硼废料铁渣碳热还原法制备零价铁并用于降解偶氮染料废水

以钕铁硼废料铁渣为原料,通过碳热还原法制备零价铁(ZVI)材料,并用于降解偶氮染料废水。考察了制备条件对ZVI性能的影响及降解条件对ZVI去除偶氮染料分子的影响。结果表明,在焙烧温度为1000℃、焙烧时间为60 min、无烟煤用量为30%(质量分数)的条件下制备的ZVI材料对甲基橙(MO)的降解性能较好。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS)对ZVI材料进行表征分析。结果表明,钕铁硼废料铁渣中的铁矿物基本被还原为ZVI,负载于铝硅酸盐上,ZVI颗粒尺寸为5~15μm。制备的ZVI材料在pH=3~10范围内对酸性橙G(OG)均具有较高的降解效率,最大去除容量为54.23 mg/g,对MO、亚甲基蓝(MB)、酸性铬兰K(ACBK)的降解效率均达到78%以上。利用碳热还原法制备ZVI不仅为钕铁硼废料铁渣的回收再利用提供了新的途径,而且为环境修复领域提供了一种低成本的降解材料。

腐植酸负载纳米零价铁对镉污染农田水稻籽粒代谢的影响

为探究腐植酸负载纳米零价铁(nZVI@HA)对镉(Cd)污染修复过程中水稻籽粒营养物质合成过程的影响,本研究采用吸附络合-液相还原法制备了一种nZVI@HA材料,同时开展水稻盆栽实验,利用电感耦合等离子体质谱及超高效液相色谱质谱技术,比较研究了nZVI@HA、纳米零价铁(nZVI)、腐植酸(HA)及nZVI与HA联合处理对Cd污染修复过程中水稻产量、籽粒中Cd含量及籽粒代谢物质组成的影响。结果表明:3组含Fe^(0)处理均可提升水稻产量、降低水稻籽粒Cd的赋存水平。尤其是在nZVI@HA作用下,水稻产量显著提升至空白组的188%、籽粒Cd含量降至0.155 mg·kg^(-1),低于我国大米Cd限量标准(0.2 mg·kg^(-1),GB 2762—2022)。代谢组学分析显示,各含Fe^(0)处理均可显著促进水稻籽粒倍他林生物合成及精氨酸和脯氨酸代谢(P<0.05且VIP>1);同时Cd污染修复过程中,水稻籽粒还可通过丙氨酸、天冬氨酸和谷氨酸代谢,核苷酸代谢,甘氨酸、丝氨酸和苏氨酸代谢,及甘油磷脂代谢特异性响应nZVI@HA处理。研究表明,nZVI@HA可特异性作用于水稻籽粒代谢过程,提升水稻抗性及产量。

无机还原剂促进铁基过氧乙酸体系中Fe(Ⅲ)还原的研究进展

铁基过氧乙酸(PAA)体系作为一种高效的高级氧化技术,近年来在水处理领域受到了广泛关注。该体系能够产生多种活性物种,显著降解水中的有机大分子,尤其在处理难降解有机物方面表现出极大优势。然而,传统的铁基PAA体系在反应过程中其限速步骤即Fe(Ⅲ)/Fe(Ⅱ)的循环极大地限制了其在大规模水处理步骤中的应用。在反应过程中,Fe(Ⅱ)被氧化为Fe(Ⅲ),然而Fe(Ⅲ)向Fe(Ⅱ)的还原转化效率降低,从而影响了整个体系的反应速度和持续性。为了确保铁基PAA体系能够持续保持高效的催化性能,研究者们提出了多种解决方案。其中最重要的一类策略是引入富电子的无机还原剂,以促进Fe(Ⅲ)向Fe(Ⅱ)的有效还原。常见的无机还原剂包括羟胺、硼、金属硫化物及碳基材料等。这些还原剂能够为Fe(Ⅲ)提供电子,加速其还原为Fe(Ⅱ),形成良性循环,增加了该体系的持续性,从而提高铁基PAA体系的整体反应效率,同时避免了添加有机还原剂引起水体总有机碳升高的问题。文章对这些无机还原剂的机理进行了详细分析。研究表明,不同的无机还原剂(均相或者非均相)在特定条件下具有独特的反应活性和适用性。文章创新性地通过系统分析不同类型无机还原剂的性能,明确了无机还原剂在加速Fe(Ⅲ)还原中的作用及其对铁基PAA体系整体反应效率提高的影响,为该体系的进一步优化提供了理论支持。总体而言,研究这些无机还原剂的作用不仅有助于优化铁基PAA体系的催化性能,还为该体系在水处理和其他环境修复领域的推广应用提供了技术支持。这些研究不仅有助于提高铁基PAA体系的反应效率,减少铁泥的产生,还方便在水处理和其他环境修复领域的应用提供了更多可能性。

钢厂酸性废水循环浸出软锰矿工艺条件研究

以钢厂酸性废水为还原剂,研究了钢厂酸性废水还原浸出软锰矿工艺,以达到综合利用软锰矿和钢厂酸性废水的目的。结果表明,在FeCl2与MnO_(2)物质的量比2.2、浸出温度90℃、浸出时间3 h、液固比11∶1、初始酸性废水浓度2.5 mol/L条件下,软锰矿中Mn、Fe、Al的浸出率分别达到97.14%、95.37%和41.33%。采用废铁屑还原浸出液中Fe^(3+),在反应温度80℃、反应时间50 min、废铁屑加入量为理论量的1.1倍时,Fe^(3+)还原率达到99.85%。Fe^(3+)还原为Fe^(2+)后,含Fe^(2+)还原液返回浸出,浸出结果稳定,其中,软锰矿中Mn、Fe、Al平均浸出率分别达到96.75%、95.31%、41.18%。

石煤钒矿酸浸提钒及酸浸液中和还原研究

开展石煤钒矿酸浸液的还原与中和不同先后顺序对钒损失及钒的还原程度的影响,及对钒离子和铁离子的价态变化规律影响的研究,为建立制备合格萃钒原液提供方法和理论指导。结果表明,与石煤钒矿酸浸液先还原后中和过程对比,先中和后还原过程的钒损失率小(<4%),还原剂Na_(2)S_(2)O_(3)用量一样,因此选择先中和后还原工艺。先以碳酸钙中和,控制中和终点pH=2.2~2.3;再以Na_(2)S_(2)O_(3)还原,1 L酸浸液用量为15.0~20.0 g,中和还原后溶液pH=2.9~3.0。由此制备出最佳萃钒原液。通过研究钒矿酸浸液中和还原过程中铁和钒的价态变化可知,无论酸浸液中和与还原二者先后顺序如何,均可判断出铁和钒的还原程度及钒的损失程度,1 L酸浸液Na_(2)S_(2)O_(3)最佳用量均为15~20 g,可作为研究钒矿酸浸液中和还原过程的辅助手段。

活性铁的制备及其处理废水的特性研究

本文优化了活性铁的制备方法,研究了利用活性铁体系各组分处理含腐植酸、铬或镍废水的特性及作用机理,并对活性铁及其反应产物进行了XRD、FTIR和SEM表征。结果表明:(1)先通氮气5 min,再摇床反应7 h所得活性铁性能最佳,零价铁表面基本被粒径为50~100 nm蓬松Fe_(3)O_(4)颗粒覆盖;(2)活性铁体系中混杂存在的Fe 0、Fe^(2+)、Fe_(3)O_(4)及其他铁(氢)氧化物对腐植酸的去除具有协同效应,原液中强化Fe^(2+),可将腐植酸的去除率从70.1%提高到99.3%;(3)活性铁体系原液对重金属铬和镍的去除效率均接近100%。六价铬的去除主要依靠零价铁与六价铬之间的氧化还原反应完成,而二价镍主要是通过活性铁中四氧化三铁的吸附及与二价铁反应形成稳定的镍氢氧化物沉淀的方式去除。