3种含铁材料对重金属和砷复合污染底泥稳定化处理

选用3种含铁材料FeCl3、Fe(OH)3和FePO4,开展重金属和砷(As)复合污染底泥的稳定化处理实验,并用毒性浸出测试(TCLP)的结果和底泥交换态重金属(Pb、Cd、Cu、Zn)及As的含量来评价其稳定化效果。结果表明,(1)FeCl3和FePO4降低了底泥pH值,Fe(OH)3轻微地提高了底泥pH值。(2)FeCl3活化了底泥中Pb、Cd、Cu、Zn,使其浸出量和交换态含量增加,对As浸出量的影响不大,但使底泥中As交换态含量明显降低,且在最大添加量(8.00 g/kg)时As交换态含量未检测出;Fe(OH)3降低了Cd交换态和浸出量,稍增加了As交换态和浸出量,但对Pb、Cu、Zn交换态和浸出量影响不明显;FePO4明显降低了Pb的浸出量和交换态含量,略微降低了交换态Cd、Zn含量,对交换态Cu影响不大,但明显增加了As的浸出量和交换态含量。综上,FeCl3对As具有较好的稳定化效果,但明显活化了底泥中的4种重金属;Fe(OH)3亦对底泥中Cd有一定稳定化效果;FePO4对Pb的稳定化效果较好,但明显活化了底泥中的As。显然,3种含铁材料都不能实现底泥中重金属和As的同时稳定化。     

冻融循环对含铁材料稳定砷污染土壤的影响

为分析冻融循环对污染土壤砷(As)的稳定化性能的影响,投加4种含铁材料(Fe SO_4、Fe S、Fe_2(SO_4)_3和Fe~0)对土壤中的As进行稳定化处理,并通过实验室模拟冻融过程,研究4种含铁材料稳定化处理后土壤中无定形氧化铁含量、氧化铁活化度、p H和As的浸出毒性随冻融循环的变化。结果表明:4种含铁材料稳定化土壤无定形氧化铁含量与氧化铁活化度随冻融循环的变化趋势基本一致;冻融循环降低了无定形氧化铁的含量,促进了铁氧化物的结晶老化。与未冻融土壤相比,冻融循环增加了稳定化土壤As的浸出毒性,但在冻融后期,As浸出毒性的增加量呈降低的趋势。4种含铁材料稳定化土壤As的浸出毒性随冻融循环表现出不同的变化趋势。1%Fe~0稳定化土壤经过冻融循环As的稳定性最高,1%Fe SO_4和1%Fe_2(SO_4)_3稳定化土壤次之,而1%Fe S稳定化土壤最低。因此,冻融循环增加了稳定化土壤As再释放的环境风险,Fe~0用做冻融地区As污染土壤稳定化药剂较为合适。     

阿散酸在土壤中的降解与形态变化

通过土壤培养实验,研究畜牧养殖过程中阿散酸污染在土壤中的降解规律和形态变化特征。设计阿散酸污染水平为0、30、75、150、225和300 mg·kg~(-1),分别于培养的2~48 h和5~60 d采集土样,测定其中砷(As)、阿散酸、水溶态As、吸附态As、铁型砷(Fe-As)、铝型砷(Al-As)、钙型砷(Ca-As)、可还原态As和残渣态As。结果表明:阿散酸水平为30~75mg·kg~(-1)时,48 h内降解率为42.99%~71.77%,40 d时降解率100%;阿散酸水平为150~300 mg·kg~(-1)时,降解较慢,降解最快时间段为5~10 d时,但60 d时各组仍有部分阿散酸未被降解;阿散酸污染水平对土壤砷形态的影响表明,随着污染水平增加,对土壤水溶态As和吸附态As影响最大,对Ca-As和残渣态As影响最小。阿散酸污染水平从30~300 mg·kg~(-1)变化时,土壤水溶态As和吸附态As分别增加了4.84~50.29倍和10.43~106.14倍;相反,Ca-As和残渣态As仅增加1.6~1.3倍和1.3~1.62倍;阿散酸污染时间对土壤砷形态的影响表明,污染后10~60 d,随着时间延长,土壤中水溶态As和交换态As呈逐渐下降趋势,而Ca-As、Fe-As和Al-As含量逐渐增加,残渣态As相对稳定。阿散酸在土壤中降解因污染水平而存在差异,低污染水平降解快,高污染水平降解慢。同时,阿散酸污染能够不同程度改变土壤各种砷形态,并随着污染时间延长,由可利用态逐渐变为稳定态。     

不同材料对高As污泥中As的固定效果

针对制酸行业产生的高砷(As)污泥浸出毒性过高且难处理的问题,选择典型无机硫化物、含钙材料、含铁或铝材料(Fe~0、铁盐、Fe_2O_3/Al_2O_3)对高As污泥进行固定化,采用醋酸(TCLP)、H_2SO_4-HNO_3和H_2O_3种浸提法评估了各材料对As的固定效果;考察了固定化对污泥中As结合态和价态分布的影响,筛选最佳固定化材料,进行联合水泥固化。结果表明,FeCl_3固化As的效果最好,3种浸提法评估的固砷率分别为86.01%、42.02%、 58.87%。FeCl_3和Fe~0处理能够促进污泥As向固定态转化,非专性和专性吸附态占比分别降低了80.60%和38.13%。FeCl_3促进非专性和专性吸附态向结晶铁锰或铁铝水化氧化物结合态和残渣态转化。CaO、Fe~0、FeSO_4·7H_2O、Fe(NO_3)_3·9H_2O、FeCl_3和Fe_2O_(12)S_3处理对As(Ⅲ)具有一定的氧化作用。FeCl_3处理后,As(Ⅲ)占比由77.14%降为19.72%。Fe(OH)_3、Fe_2O_3和Al_2O_3处理对As(Ⅲ)的氧化性不明显,Na_2S·9H_2O处理使As(Ⅲ)占比升至85.84%。随FeCl_3、水泥和两者配伍材料投加量的增加,在3种方法中,污泥中As的浸出量均明显降低,单一FeCl_3和配伍固砷效果均优于水泥;水泥配伍比≥100%时的固砷效果优于单一FeCl_3;250%FeCl_3+125%水泥可使3种方法中浸出砷浓度降至最低,分别为113.81、399.28、347.27 mg·L~(-1),固砷率均高于97%。本研究结果可为高As污泥的固定化提供参考。供参考。     

铬污染土壤的还原稳定化修复

以湖南某工业场地的铬污染土壤为修复对象,投加不同比例的Fe SO4·7H2O、Fe SO4·7H2O和Ca(OH)2混合物及Na HSO3,通过测定土壤及浸出液中六价铬、总铬以及铬的形态,比较3种稳定剂对该污染土壤的还原稳定化作用。结果表明,Fe SO4·7H2O和Na HSO3对铬污染土壤的还原稳定效果都较好,可以有效还原土壤中六价铬并能降低土壤中总铬的浸出浓度。当Fe SO4·7H2O投加量为2%时,土壤六价铬和总铬浸出浓度降幅分别达到99.0%和57.5%;当Na HSO3投加量为0.8%时,六价铬和总铬浸出浓度降幅分别达到97.7%和42.2%,与前二者相比,Fe SO4·7H2O和Ca(OH)2混合物还原稳定化效果较差。投加Fe SO4·7H2O能够将土壤中活性大的可交换态和碳酸盐态铬转化为稳定的有机态和残渣态铬;而Na HSO3主要将可交换态和碳酸盐态铬转化为相对稳定的铁锰氧化态铬,其稳定化效果要差于Fe SO4·7H2O。     

芬顿和氯化铁协同修复三价砷污染土的稳定化效果

由于铁盐稳定化修复砷污染土通常不考虑砷价态对毒性和迁移性的影响,导致了修复效果欠佳。针对三价砷污染土提出了预氧化-稳定化协同修复方法,先使用芬顿将三价砷氧化为低迁移性的五价砷,再利用氯化铁将其稳定化。通过合成沉降淋滤试验、生物可利用性、pH测试、连续萃取试验和光谱分析研究了协同修复的稳定化效果和机理。结果表明,与未经处理的污染土相比,1%用量的芬顿和1倍铁砷比的氯化铁进行协同修复的稳定化处理可使浸出浓度降低99.6%,生物可利用性砷的质量分数降低99.4%,修复效率得到提高;芬顿氧化和氯化铁稳定化都使土壤pH降低,但1倍铁砷比下协同修复后的pH为5.82,高于6倍铁砷比下只用氯化铁修复的pH (3.78),由此可一定程度上避免过量使用铁盐造成的土壤酸化;连续萃取试验表明协同修复后更多不稳定态的砷转变为稳定形态;光谱分析发现协同修复可以将土壤中三价砷全部氧化为五价,并通过铁氧化物/氢氧化物吸附和砷酸铁沉淀的形式固定砷。本研究结果可为三价砷污染土修复提供理论和技术支持。     

矿区含砷尾矿及废渣稳定化研究

通过"硫酸-硝酸法"浸出实验,以砷的浸出浓度为控制指标,选用Fe Cl2为稳定药剂,对矿区砷渣进行药剂稳定化研究。考察Fe/As摩尔比、p H值、粒度、温度及稳定时间对砷浸出浓度的影响,通过研究稳定化前后砷形态的变化,探讨重金属迁移转化规律。结果表明:砷浸出浓度随Fe Cl2投加量增加而降低,当Fe/As摩尔比为1,p H=6.5~7.5时,常温下稳定化1 h后,砷浸出浓度低于2.5 mg/L且基本达到稳定,达到《危险废物填埋污染控制标准》(GB 18598-2001)的入场要求;随反应温度升高,砷浸出浓度略有升高;矿渣稳定化处理后,砷从生物有效性高和毒性大的形态逐渐转化为毒性小、稳定性强的形态,但矿物组成和化学组成不同,砷形态的迁移转化也略有不同。     

金矿区高浓度砷污染土壤的稳定化处理

以粉煤灰、干化污泥、粉碎花生壳、硫酸亚铁(Fe_2SO_4)和磷酸二氢钾(KH_2PO_4)为稳定剂对矿区高浓度As污染土壤进行处理,通过土壤理化性质、重金属形态和浸出浓度变化等综合评估稳定剂对高浓度砷污染土壤的稳定化处理效果。结果表明,添加稳定剂可以提高土壤pH值、有机质含量和阳离子交换量。粉煤灰、干化污泥、粉碎花生壳、硫酸亚铁对土壤中的As有较好的稳定化作用,其中硫酸亚铁对土壤中As的稳定效果最好。同时添加10%粉煤灰、10%干化污泥和1%硫酸亚铁后,土壤中可交换态As、碳酸盐结合态As、铁锰氧化物结合态As、有机结合态As含量显著降低,降幅分别为62.3%、55.2%、29.6%、58.2%,残渣态As含量增加8.1%。添加粉煤灰、干化污泥、硫酸亚铁能显著降低土壤中As的浸出浓度,而添加KH_2PO_4会使土壤中As浸出浓度增加,移动性增强。当同时添加10%粉煤灰、10%干化污泥、1%粉碎花生壳和1%硫酸亚铁后,As浸出浓度最低(0.93 mg·L~(-1)),稳定效果最好,稳定化效率达到了74.8%。土壤中As的浸出浓度与可交换态As和碳酸盐结合态As呈显著正相关,与残渣态As呈显著负相关,可交换态As、碳酸盐结合态As和残渣态-As含量是影响土壤中As浸出浓度变化的主要因素。     

石灰干化污泥对土壤重金属稳定化处理的效果

以采自湖南省嘉禾县重金属复合污染土壤为研究对象,采用城市污水处理石灰干化污泥作为稳定剂,对污染土壤进行稳定化处理,并采用TCLP和BCR连续提取法对稳定化效果进行分析和评价。研究结果表明,单独使用石灰干化污泥,TCLP浸出浓度随着干化污泥质量分数的增加而显著减少,干化污泥的质量分数为40%时,稳定化率最大为Zn-98.92%、Cd-99.06%、Pb-96.84%;但是干化污泥的高pH值导致稳定后土壤中As的浸出增加。为了恢复植物生长功能,经过亚铁盐和磷酸调节pH后,石灰干化污泥稳定过的土壤pH有效降低,同时亚铁盐和磷酸有利于促进Pb和Zn的稳定效果;但是对Cd的稳定有负面影响;另外,亚铁盐的加入同时可以减少As的浸出浓度。经处理后土壤中重金属形态由不稳定态转为稳定态,使重金属的浸出浓度明显降低,减少了土壤重金属的浸出毒性。该研究结果表明,石灰干化污泥可以作为资源回收利用,应用于重金属污染土壤的修复中,并能改善稳定后土壤适宜植物生长的理化性质。     

几种含磷材料对紫色土铅稳定条件优化及磷淋失环境风险评价

以西南地区广泛分布的紫色土-灰棕紫泥为对象,探讨了磷酸二氢钾(MPP)、过磷酸钙(SSP)、钙镁磷肥(CMP)和磷矿粉(PR)4种含磷材料,在不同剂量下对不同程度Pb污染土壤的稳定化效果,并对其长期稳定性和P淋失的环境风险进行了研究。结果表明4种含磷材料对土壤Pb均具有显著稳定化效果。在P:Pb(摩尔比)为1时,稳定效率相对大小顺序:MPPSSPěCMPPR。当Pb污染浓度600 mg·kg~(-1)时,4种稳定剂均能实现土壤Pb的稳定化。当Pb浓度ě1 200 mg·kg~(-1)时,MPP依然保持高效的稳定化能力,但是PR对土壤稳定化不能满足浸出标准。固定Pb污染浓度为1 200 mg·kg~(-1),含磷材料稳定化Pb的效果受其剂量的影响。MPP在P:Pb为1时稳定化处理3 d即可达到浸出标准,SSP和CMP在P:Pb为1.5和2时稳定化处理30 d可达到浸出标准,PR在P:Pb为4时稳定化处理60 d基本达到浸出标准,增加稳定剂剂量能够显著提高对紫色土Pb的稳定速率。施用系列含磷材料稳定剂后,除SSP外均使土壤pH升高,且随着稳定时间的延长,土壤中可交换态(Exc-Pb)逐渐降低,残渣态(Res-Pb)所占比例逐渐升高。满足Pb浸出标准的处理在稳定化9个月内土壤中Pb浸出浓度始终维持在极低水平,并且土壤有效P也一直保持在土壤P淋失临界值以内,说明合理剂量和类型的含磷材料能满足持续稳定化和环境风险控制要求。     

Effects of plant arsenic uptake and heavy metals on arsenic distribution in an arsenic-contaminated soil

This study examined the effects of heavy metals and plant arsenic uptake on soil arsenic distribution. Chemical fractionation of an arsenic-contaminated soil spiked with 50 or 200mg kg(-1) Ni, Zn, Cd or Pb was performed before and after growing the arsenic hyperaccumulator Pteris vittata L for 8weeks using NH(4)Cl (water-soluble plus exchangeable, WE-As), NH(4)F (Al-As), NaOH (Fe-As), and H(2)SO(4) (Ca-As). Arsenic in the soil was present primarily as the recalcitrant forms with Ca-As being the dominant fraction (45%). Arsenic taken up by P. vittata was from all fractions though Ca-As contributed the most (51-71% reduction). After 8weeks of plant growth, the Al-As and Fe-As fractions were significantly (p<0.01) greater in the metal-spiked soils than the control, with changes in the WE-As fraction being significantly (p=0.007) correlated with plant arsenic removal. The plant's ability to solubilize soil arsenic from recalcitrant fractions may have enhanced its ability to hyperaccumulate arsenic.     

Removal of PCBs in contaminated soils by means of chemical reduction and advanced oxidation processes

Although the chemical reduction and advanced oxidation processes have been widely used individually, very few studies have assessed the combined reduction/oxidation approach for soil remediation. In the present study, experiments were performed in spiked sand and historically contaminated soil by using four synthetic nanoparticles (Fe⁰, Fe/Ni, Fe₃O₄, Fe_3???x Ni _x O₄). These nanoparticles were tested firstly for reductive transformation of polychlorinated biphenyls (PCBs) and then employed as catalysts to promote chemical oxidation reactions (H₂O₂ or persulfate). Obtained results indicated that bimetallic nanoparticles Fe/Ni showed the highest efficiency in reduction of PCB28 and PCB118 in spiked sand (97 and 79 %, respectively), whereas magnetite (Fe₃O₄) exhibited a high catalytic stability during the combined reduction/oxidation approach. In chemical oxidation, persulfate showed higher PCB degradation extent than hydrogen peroxide. As expected, the degradation efficiency was found to be limited in historically contaminated soil, where only Fe⁰ and Fe/Ni particles exhibited reductive capability towards PCBs (13 and 18 %). In oxidation step, the highest degradation extents were obtained in presence of Fe⁰ and Fe/Ni (18–19 %). The increase in particle and oxidant doses improved the efficiency of treatment, but overall degradation extents did not exceed 30 %, suggesting that only a small part of PCBs in soil was available for reaction with catalyst and/or oxidant. The use of organic solvent or cyclodextrin to improve the PCB availability in soil did not enhance degradation efficiency, underscoring the strong impact of soil matrix. Moreover, a better PCB degradation was observed in sand spiked with extractable organic matter separated from contaminated soil. In contrast to fractions with higher particle size (250–500 and <500 μm), no PCB degradation was observed in the finest fraction (≤250 μm) having higher organic matter content. These findings may have important practical implications to promote successively reduction and oxidation reactions in soils and understand the impact of soil properties on remediation performance.     

Influence of amendments on soil arsenic fractionation and phytoavailability by Pteris vittata L

Increasing availability of soil arsenic is of significance for accelerating phytoremediation efficiency of As-polluted sites. The effects of seven amendments, i.e., citrate, oxalate, EDTA, sodium polyacrylate (SPA), phosphate rock (PR), single superphosphate (SSP), and compost on fractionation and phytoavailability of soil As were investigated in lab culture experiment. The results showed that the addition of PR, SPA, EDTA or compost to soils significantly increased the concentration of NaHCO₃-extractable As over a 120 d incubation period compared with the control (amendment-free) soil. Then, the four amendments were selected to add to As-contaminated soil growing Pteris vittata. It was concluded that As accumulation by the fern increased significantly under the treatments of PR and SPA by 25% and 31%, respectively. For As fractionation in soil, SPA increased Fe-As significantly by 51% and PR increased Ca-As significantly by 18%, while both the two amendments reduced occluded-As by 16% and 19%, respectively. Adding PR and SPA in soil increased the activities of urease and neutral phosphatase resulting from the improvement the fertility and physical structure of the soil, which benefits plant growth and As absorption of P. vittata. The results of the research revealed that both PR and SPA were effective amendments for improving phytoremediation of As-contaminated sites by P. vittata.     

Degradation of bisphenol A in aqueous solution by persulfate activated with ferrous ion

Degradation of bisphenol A (BPA) in aqueous solution was studied with high-efficiency sulfate radical (SO₄ ^?·), which was generated by the activation of persulfate (S₂O₈ ^2?) with ferrous ion (Fe²⁺). S₂O₈ ^2? was activated by Fe²⁺ to produce SO₄ ^?·, and iron powder (Fe⁰) was used as a slow-releasing source of dissolved Fe²⁺. The major oxidation products of BPA were determined by liquid chromatography-mass spectrometer. The mineralization efficiency of BPA was monitored by total organic carbon (TOC) analyzer. BPA removal efficiency was improved by the increase of initial S₂O₈ ^2? or Fe²⁺ concentrations and then decreased with excess Fe²⁺ concentration. The adding mode of Fe²⁺ had significant impact on BPA degradation and mineralization. BPA removal rates increased from 49 to 97 % with sequential addition of Fe²⁺, while complete degradation was observed with continuous diffusion of Fe²⁺, and the latter achieved higher TOC removal rate. When Fe⁰ was employed as a slow-releasing source of dissolved Fe²⁺, 100 % of BPA degradation efficiency was achieved, and the highest removal rate of TOC (85 %) was obtained within 2 h. In the Fe⁰–S₂O₈ ^2? system, Fe⁰ as the activator of S₂O₈ ^2? could offer sustainable oxidation for BPA, and higher TOC removal rate was achieved. It was proved that Fe⁰–S₂O₈ ^2? system has perspective for future works.     

Study on the removal of elemental mercury from simulated flue gas by Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-CeO<Subscript>2</Subscript>/AC at low temperature

Fe₂O₃ and CeO₂ modified activated coke (AC) synthesized by the equivalent-volume impregnation were employed to remove elemental mercury (Hg⁰) from simulated flue gas at a low temperature. Effects of the mass ratio of Fe₂O₃ and CeO₂, reaction temperature, and individual flue gas components including O₂, NO, SO₂, and H₂O (g) on Hg⁰ removal efficiency of impregnated AC were investigated. The samples were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with optimal mass percentage of 3 % Fe₂O₃ and 3 % CeO₂ on Fe3Ce3/AC, the Hg⁰ removal efficiency could reach an average of 88.29 % at 110 °C. Besides, it was observed that O₂ and NO exhibited a promotional effect on Hg⁰ removal, H₂O (g) exerted a suppressive effect, and SO₂ showed an insignificant inhibition without O₂ to some extent. The analysis of XPS indicated that the main species of mercury on used Fe3Ce3/AC was HgO, which implied that adsorption and catalytic oxidation were both included in Hg⁰ removal. Furthermore, the lattice oxygen, chemisorbed oxygen, and/or weakly bonded oxygen species made a contribution to Hg⁰ oxidation.     

空速和二氧化碳对沼气脱硫剂硫容确定的影响

为了弄清空速与二氧化碳含量对氧化铁脱硫剂硫容确定的影响,分别在实验气源为纯硫化氢,空速为40、80、120和160 h-1以及实验气源为二氧化碳含量分别在0%、20%、40%和80%,其余为硫化氢,空速为80 h-1条件下,对T502(粗脱硫剂)和HXT-2(精脱硫剂)2种氧化铁脱硫剂进行了不同测试条件对氧化铁硫容确定影响的研究。研究结果表明,T502和HXT-2氧化铁脱硫剂硫容测试结果随着空速和二氧化碳含量增加而减少,结果显示了在空速较低条件下(120h-1),二氧化碳含量在40%以下时对氧化铁脱硫剂硫容测试结果影响不大,但二氧化碳含量在40%以上时,对氧化铁脱硫剂硫容测试结果影响显著。     

Ozone-enhanced catalytic oxidation of monochlorobenzene over iron oxide catalysts

In this study, we examined the experimental catalytic oxidation of gaseous monochlorobenzene (MCBz) with O₃ over Fe₂O₃ in a packed bed reactor to investigate the feasibility of economical low temperature decomposition at a high space velocity (SV). We investigated the effects of several reaction parameters (temperature, O₃ concentration, and SV) on the MCBz oxidation. At 150 °C, the conversion of MCBz over Fe₂O₃ in the absence of O₃ was only 3%; it increased to 91% over Fe₂O₃ in the presence of 1200 ppm of O₃ at a high SV of 83 s⁻¹. A long-term operation study revealed that the conversion of MCBz was stable for more than 96 h. In the steady state, the carbon and chlorine balances were 88% and 86%, respectively. Applying a Langmuir-Hinshelwood kinetic model, we estimated an activation energy of 16.7 kJ mol⁻¹ for MCBz oxidation over Fe₂O₃ in the presence of O₃.     

Toxicity of TiO2, ZrO2, Fe,Fe2O3, and Mn2O3 nanoparticles to the yeast, Saccharomyces cerevisiae

The growing application of engineered nanomaterials is leading to an increased occurrence of nanoparticles (NPs) in the environment. Thus, there is a need to better understand their potential impact on the environment. This study evaluated the toxicity of nanosized TiO₂, ZrO₂, Fe⁰, Fe₂O₃, and Mn₂O₃ towards the yeast Saccharomyces cerevisiae based on O₂ consumption and cell membrane integrity. In addition, the state of dispersion of the nanoparticles in the bioassay medium was characterized.     

高压电弧放电处理偶氮染料废水

用高压电弧放电产生的低温等离子体对含偶氮染料的废水进行了处理，以甲基橙为例研究了电压幅值、处理时间、溶液初始浓度、溶液初始pH值、投加Fe^2＋和Fe^3＋对染料脱色的影响。实验结果表明，甲基橙浓度为50mg／L时其降解率随时间和电压幅值的增加而增加。溶液初始浓度对染料去除效果影响较为明显，同等条件下初始浓度越低降解率越高。酸性条件下有利于低温等离子体处理甲基橙。Fe^2＋和Fe^3＋对低温等离子体降解甲基橙有一定的催化作用。电压8kV处理3min，Fe^2＋为20mg／L时去除率由89．64％增至99．72％。Fe2（SO4），的最佳投加量为5mg／L（以Fe^3＋计），而FeCl，的最佳投加量为80mg／L（以Fe^3＋计）。