1、活性炭吸附活性炭吸附ADSORPTIONAbsorption: the process of accumulating substances that are in solution on a suitable interface.Absorbate: the substance that is being removed from the liquid phase at the interface.Absorbent: the solid, liquid or gas phase onto which the adsorbate accumulates.Adsorption is used

2、in drinking water treatment to remove organic contaminants:Taste and odor-causing chemicalsSynthetic organic chemicalsColor forming organicsSome disinfection by-produce precursorsAdsorption is used in wastewater treatment as a polishing process for water that has already received normal biological t

3、reatment to remove a portion of the remaining dissolved organic matter.Historical Development一、 吸附原理 吸附劑：固體表面有吸附水中溶解及膠體物質(zhì)的吸附劑：固體表面有吸附水中溶解及膠體物質(zhì)的能力能力,比表面積很大的活性炭等具有很高的吸附能力。比表面積很大的活性炭等具有很高的吸附能力。吸附劑吸附劑 粉末狀活性炭粉末狀活性炭 粒狀活性炭（園柱狀、球狀），粒徑粒狀活性炭（園柱狀、球狀），粒徑24mm主要有活性炭、磺化煤、沸石、硅藻土、焦炭、木炭等。主要有活性炭、磺化煤、沸石、硅藻土、焦炭、木炭等。活性炭的

4、制造活性炭的制造木材、煤、果殼木材、煤、果殼高溫炭化高溫炭化隔絕空氣，隔絕空氣，600炭渣炭渣活性炭活性炭活化活化,800900活化劑：活化劑：ZnCl2蒸汽高溫活化蒸汽高溫活化 1.比表面積比表面積 每每g活性炭所具有的表面積。活性炭的比表面積為：活性炭所具有的表面積。活性炭的比表面積為：5001700m2/g，99.9%的表面積在多孔結(jié)構(gòu)顆粒的內(nèi)部。的表面積在多孔結(jié)構(gòu)顆粒的內(nèi)部。活性炭的細孔構(gòu)造和分布活性炭的細孔構(gòu)造和分布2.細孔構(gòu)造細孔構(gòu)造 小孔：小孔：2nm，0.150.90mL/g，占比表面積的，占比表面積的95%以上，起吸附作用，吸附以上，起吸附作用，吸附量以小孔吸附為主。量以小孔

5、吸附為主。過渡孔：過渡孔：2100nm，0.020.10mL/g，占比表面積，占比表面積25 n mMesopores 1 nm and 25nmMicropores 1 nmPowdered activated carbon (PAC): with a diameter of less than 0.074mm (200 sieve)Granular activated carbon (GAC): with a diameter of greater than 0.1mm (140 sieve) GACPACTotal surface aream2/g700-1300800-1800Bulk

6、 densityKg/m3400-500360-740Particle density, wetted in waterKg/L1.0-1.51.3-1.4Particle size range0.1-2.36 mm5-50 mAsh % 8 6Moisture as packed%2-83-10二、影響吸附的因素衡量衡量指標指標吸附能力吸附能力吸附速度吸附速度固體吸附劑用吸附量衡量固體吸附劑用吸附量衡量單位質(zhì)量吸附劑在單位單位質(zhì)量吸附劑在單位時間內(nèi)所吸附的物質(zhì)量時間內(nèi)所吸附的物質(zhì)量吸附吸附階段階段顆粒外部顆粒外部擴散階段擴散階段孔隙擴散孔隙擴散階段階段吸附反應(yīng)吸附反應(yīng)階段階段吸附質(zhì)從溶液中擴

7、散到吸附吸附質(zhì)從溶液中擴散到吸附劑表面劑表面吸附質(zhì)在吸附劑孔隙中繼續(xù)吸附質(zhì)在吸附劑孔隙中繼續(xù)向吸附點擴散向吸附點擴散吸附質(zhì)被吸附在吸附劑孔隙吸附質(zhì)被吸附在吸附劑孔隙內(nèi)的吸附點表面內(nèi)的吸附點表面吸附速度主要取決于外部擴散速度和孔隙擴散速度。吸附速度主要取決于外部擴散速度和孔隙擴散速度。外部擴外部擴散速度散速度與溶液濃度成正比與溶液濃度成正比與吸附劑的比表面積的大小成正與吸附劑的比表面積的大小成正比比吸附劑顆粒直徑越小，速度越快吸附劑顆粒直徑越小，速度越快增加溶液與顆粒間的相對運動速度，增加溶液與顆粒間的相對運動速度，可提高速度可提高速度孔隙擴孔隙擴散速度散速度吸附劑顆粒越小，速度越快吸附劑顆粒越

8、小，速度越快對于同一種活性炭，在恒定溫度下平衡吸附量對于同一種活性炭，在恒定溫度下平衡吸附量x/m僅是平僅是平衡濃度衡濃度 e的函數(shù)，此時的函數(shù)，此時x/m與與 e的關(guān)系稱為等溫吸附線。的關(guān)系稱為等溫吸附線。初始濃度初始濃度 i容積容積V活性炭活性炭質(zhì)量質(zhì)量m開始開始平衡濃度平衡濃度 e容積容積V活性炭活性炭質(zhì)量質(zhì)量m平衡平衡到達吸附平衡時，單位到達吸附平衡時，單位質(zhì)量活性炭的吸附量為質(zhì)量活性炭的吸附量為mVmxei)(對于一種活性炭來說，實驗證明對于一種活性炭來說，實驗證明x/m值是平衡濃度值是平衡濃度 e和溫度的函數(shù)和溫度的函數(shù)對于特定的活性炭于特定的原水，對于特定的活性炭于特定的原水，x

9、/m與與 e的函數(shù)是一定的。的函數(shù)是一定的。Langmuir 吸附等溫線吸附等溫線eebmxbmx1)/(0BET 吸附等溫線吸附等溫線)/)(1(1)()/(0seeseBmxBmxFreundlich 吸附等溫線吸附等溫線nefKmx/1x/m ex/m eSurface layerMultiple layerx/m eExample:A tricholoroethene (TCE) isotherm was performed on Calgon F400 GAC. A total of 25 isotherm points were determined using 250-ml am

10、ber bottles with Teflon-lined screw caps. The dosage of GAC varied in each bottle. The GAC used was powdered from virgin stock GAC, washed, and dried to a constant weight before use. Pure TCE was added to a solution containing organic free laboratory water to yield a TCE initial concentration of abo

11、ut 10,000 g/L. The weight of the bottles and the caps were recorded prior to filling the bottles with GAC dosage and the TCE solution. The bottles were filled headspace free to prevent any TCE from volatizing out of the solution. A total of eight extra empty bottles were filled and allowed to equili

12、brate. The extra bottles were used as blanks to measure the initial concentration used in the isotherm. All the bottles were placed on a rotating device and rotated at 25 rev/min for a period of 14 days. The bottles were then removed from the tumbler and the carbon was allowed to settle for a few ho

13、urs, and a sample was drawn from each bottle and the TCE concentration was analyzed using a gas chromatograph. Based on the raw data given below, calculate the average initial liquid-phase concentration from the equilibrated blanks and the equilibrium adsorbent-phase concentration. Plot the correspo

14、nding values of qe and Ce on arithmetic and log-log paper to determine the nature of the distribution. A summary of the GAC dosages, solution volume, and equilibrated blanks is provided below:Example:p Experimental data: Carbon type: F-400 Temperature: 13 C Chemical: TCE pH:6.8 Carbon size: 200 400S

15、ample No.Dosage D, gVolume V,mlTCE Liquid-Phase concentration Ce, g/L10.44254247.1320.39002251.24.530.34427252.54.140.26784252.48.150.20674253.615.560.18305251.118.970.16521251.424.580.14041252.174.390.12416252.157100.10836249.6109110.09418254.7162.5120.08320253.0213.6130.07332251.0144.9140.05380251

16、.2643.1150.04752255.1872.6160.03956252.31109.1170.03315251.51476.9180.02696255.12699.8190.02189254.63271.9200.01609253.04858.4210.01072251.76263.2220.00544251.58427.3230.00343252.310009.8240.00164252.99875.5250.06273253.0352.6p Equilibrated blank data:Sample No.Equilibrated Blank C0, g/L110,48628,40

17、1311,355410,205510,415612,912712,025811,123p isotherm datasolution:1. Calculate the average initial TCE aqueous-phase concentration in g/L: LgC/865,108123,11025,12912,12415,10205,10355,11401, 8486,1002. Calculate the equilibrium adsorbent-phase concentration in g/g. The required computations for sam

18、ple 1 is shown below:ggLggLCMVqee/6065/)3865,10(44254. 02471. 0)1 (865,10) 1 () 1 () 1 (/)865,10()(0LgCMVCCMVqeeeSample No.Ce, g/Lqe, g/g136065.024.5699.534.17966.048.110231.0515.513309.0618.914877.8724.516496.4874.319374.795721945.61010924776.411162.528944.612213.632390.313144.936699.6Sample No.Ce,

19、 g/Lqe, g/g14643.147728.915872.653643.6161109.162221.6171476.971227.2182699.877263.3193271.988317.9204858.494452.8216263.2108054.9228427.3112712.72310009.8249875.525352.642339.3solution:3. Plot the TCE isotherm data on arithmetic and log-log paper.Arithmetic log-log推導(dǎo)的基本假定推導(dǎo)的基本假定吸附劑表面吸附劑表面吸附層厚度吸附層厚度

20、被吸附水分子被吸附水分子未被吸附水分子未被吸附水分子未被吸附物質(zhì)分子未被吸附物質(zhì)分子被吸附物質(zhì)分子被吸附物質(zhì)分子假定被吸附的水分子和物質(zhì)顆粒的數(shù)目分別為假定被吸附的水分子和物質(zhì)顆粒的數(shù)目分別為n1s和和n2s個；未被吸附的水分子和物質(zhì)個；未被吸附的水分子和物質(zhì)顆粒的數(shù)目分別為顆粒的數(shù)目分別為n1和和n2個個由于水分子與吸附顆粒大小相同，單位吸附劑表面的吸附點位一定（由于水分子與吸附顆粒大小相同，單位吸附劑表面的吸附點位一定（ n1s+n2s =n，單，單位吸附劑表面共有位吸附劑表面共有n個個 0面積），單位吸附劑表面所能容納的顆粒總數(shù)是一定的。面積），單位吸附劑表面所能容納的顆粒總數(shù)是一定的。

21、吸附劑表面上吸附與脫落過程相平衡吸附劑表面上吸附與脫落過程相平衡未被吸附的物質(zhì)顆粒數(shù)目未被吸附的物質(zhì)顆粒數(shù)目+ +被吸附的水分子數(shù)目被吸附的水分子數(shù)目被吸附的物質(zhì)顆粒數(shù)目被吸附的物質(zhì)顆粒數(shù)目+ +未被吸附的水分子數(shù)目未被吸附的水分子數(shù)目即即n2+ n1sn2s+ n1n2+ n1sn2s+ n1上式得到平衡常數(shù)上式得到平衡常數(shù)2112nnnnKssnnnss21ssnnnnnK2221)(1/nKb snnbnnb222)1 (2221nbnnbns除以除以Avogadro常數(shù)常數(shù)LnbLnmxbmx2201)/(Lne2b=bLeebmxbmx1)/(01、求吸附公式的常數(shù)、求吸附公式的常數(shù)

22、-圖解法圖解法Langmuir 公式公式00)/(11)/(1)/(1mxmxbmxe00)/(1)/(1)/(mxbmxmxee(x/m)01/b(x/m)0O1/ e1/(x/m)1/b(x/m)01/(x/m)0O e e /(x/m) e1eebmxbmx1)/(0BET公式公式)/)(1(1)()/(0seeseBmxBmx00)/(1)/(1)/)(mxBmxBBmxseese(B-1)/(x/m)0O e / s e /( s- e)( x/m)(B-1)/B(x/m)0 s值估計偏高值估計偏高 s值估計偏低值估計偏低未知未知Freundlich公式公式feKnmxlglg1lg

23、nefKmx/1線性化線性化lgKf1/nOlg elg(x/m)Example: Determination of Freundlich and Langmuir isotherm parametersFor the experimental isotherm data given below, determine the Freundlich and Langmuir isotherm parameters. Apply linear regression to determine the isotherm parameters. Solution:p Experimental data:

24、 Carbon type: F-400 Temperature: 13 C Chemical: TCE pH:7.5-8 Carbon size: 200 400 Equilibrium time: 31daysSample No.CA, mole/LqA, mole/g123.673726.6745033.2631840.32212150.16985.260.11475.81. Determine Langmuir isotherm parameters.1/(x/m)0=slope=0.0013g/ mole(x/m)0=769.23 mole/g=1.01 105 g/g1/b(x/m)

25、0=intercept=0.0033g/Lb =3.00 10-3L/ gExample: Determination of Freundlich and Langmuir isotherm parametersFor the experimental isotherm data given below, determine the Freundlich and Langmuir isotherm parameters. Apply linear regression to determine the isotherm parameters. Solution:2. Determine Fre

26、undlich isotherm parameters.1/n=slope=0.4327lg Kf=intercept=2.28314327. 04327. 04327. 0)(68.60)100039.131(1000139.1319 .191)(9 .191mgLgmgmgggmolemoleLgmgmoleggmolemoleLgmoleKfFreundlich isotherm equation provides a better fit of the data than the Langmuir model.Powdered activated carbonPowdered acti

27、vated carbon is primarily used in the treatment of taste and odor compounds and the treatment of low concentrations of pesticides and other organic micropollutants. The convenience of PAC is that it can be employed periodically in a conventional treatment plant with minimum capital cost. For example

28、, PAC can be used during summer months for surface water sources containing taste and odor compounds resulting from algal blooms. It is also be employed to remove chemical pollution (pesticides and herbicides) carried in spring runoff.Factors that influence PAC performance Location of PAC additionTh

29、e most promising locations for PAC addition: (1) at the raw-water intake, (2) in the rapid-mix tank, and (3) in a slurry contactor (separately designed for PAC).Point of additionAdvantages disadvantagesPowdered activated carbonFactors that influence PAC performance impact of disinfectants and oxidan

30、ts on PAC performanceFor the removal of MIB and geosmin, oxidants such as chlorine and potassium permanganate have a negative impact on PAC removal of taste and odor compounds. The impact is the greatest when oxidants is added simultaneously with the PAC.For example, when oxidants is added with PAC,

31、 removal efficiencies for MIB decrease by as much as 50-75%; while geosmin can decrease by as much as 20-40%. impact of organic matter on PAC performanceBy either pore blockage or competing for adsorption sites, OM can reduce the adsorption capacity of micropollutants in PAC. Consequently, single-so

32、lute isotherms performed in organic free water will predict a higher capacity than would be observed for PAC dosages in natural water containing OM. impact of contact time on PAC performanceTypically, PAC added in a conventional plant has contact times between 0.5 and 2h, which is not sufficient to

33、utilize fully the capacity of the PAC for micropollutants. For example, it was reported that for 90% removal of atrazine, the contact time could be decreased from 4h to 30min if the PAC dosage was increased from 23 to 32 mg/L.吸附公式的直接應(yīng)用必須是吸附過程在較短時間內(nèi)達到平衡，一般應(yīng)用于粉末活性炭吸附公式的直接應(yīng)用必須是吸附過程在較短時間內(nèi)達到平衡，一般應(yīng)用于粉末活性炭

34、例題：廢水中含有機物的濃度為例題：廢水中含有機物的濃度為20mg/L，用粉末活性炭做吸附試驗，吸附迅速達到平衡，用粉末活性炭做吸附試驗，吸附迅速達到平衡，數(shù)據(jù)用數(shù)據(jù)用Langmuir公式處理后得出公式處理后得出b=0.13L/mg，(x/m)0=0.345mg/mg。按。按CSTR處理考慮，處理考慮，池子容積為池子容積為60000升，流量為升，流量為100L/s,出水有機物濃度要求不超過出水有機物濃度要求不超過1mg/L。在開始運行時，。在開始運行時，先按反應(yīng)器容積每升加活性炭先按反應(yīng)器容積每升加活性炭20g，流出的活性炭經(jīng)分離后在回流到反應(yīng)器，直到完全飽，流出的活性炭經(jīng)分離后在回流到反應(yīng)器，

35、直到完全飽和后再補充新炭，計算每秒鐘補充的活性炭量。和后再補充新炭，計算每秒鐘補充的活性炭量。解：按解：按Langmuir公式求公式求 e=1.0mg/L時的時的x/m值值)/(0397. 0113. 011345. 013. 01)/(0mgmgbmxbmxee令每秒鐘投加的活性炭的量為令每秒鐘投加的活性炭的量為Mmg，因投加的新活性炭故，因投加的新活性炭故(x/m)0=0值，有物料恒算值，有物料恒算100(20-1)=M(0.0397-0)M=1900/0.0397=47858mg/s=47.9g/s每每mg活性炭對有機物的吸附潛力為活性炭對有機物的吸附潛力為0.345mg，而實際中只利用

36、了，而實際中只利用了0.0397mg例題：廢水中含有機物的濃度為例題：廢水中含有機物的濃度為20mg/L，用粉末活性炭做吸附試驗，吸附迅速達到平衡，用粉末活性炭做吸附試驗，吸附迅速達到平衡，數(shù)據(jù)用數(shù)據(jù)用Langmuir公式處理后得出公式處理后得出b=0.13L/mg，(x/m)0=0.345mg/mg。按。按CSTR處理考慮，處理考慮，池子容積為池子容積為60000升，流量為升，流量為100L/s,出水有機物濃度要求不超過出水有機物濃度要求不超過1mg/L。在開始運行時，。在開始運行時，先按反應(yīng)器容積每升加活性炭先按反應(yīng)器容積每升加活性炭20g，按下圖所示的逆流吸附操作，計算每秒鐘補充的活性，

37、按下圖所示的逆流吸附操作，計算每秒鐘補充的活性炭量。炭量。 1CSTR1(x/m)1解：解：CSTR2的平衡濃度的平衡濃度 2=1.0mg/L時的時的(x/m)2=0.0397mg/mg20mgL-1100L/sM/ gs-1x/m 2CSTR2(x/m)2 1/mgL-1M/ gs-1(x/m)21mgL-1M/ gs-10100L/s在第二個在第二個CSTR中只有進水的有機物濃度中只有進水的有機物濃度 1未知，對未知，對CSTR2中的有機物做物料恒算中的有機物做物料恒算LmgM/) 11000397. 0(1 1是是CSTR1中平衡濃度，由此可求中平衡濃度，由此可求CSTR1中的吸附量中的

38、吸附量) 11000397. 0(13. 01) 11000397. 0(345. 013. 0)(1MMmxCSTR1中的有機物做物料恒算中的有機物做物料恒算將將(x/m)1和和 (x/m)2帶入上式帶入上式Mmxmx)()()20(100211MMMM0397. 0) 11000397. 0(13. 01) 11000397. 0(345. 013. 0)11000397. 0(20100解上式得解上式得M=12550mg/s=12.5g/s吸附柱的設(shè)計通常是在已知活性炭的吸附性能、運行負荷和吸附柱高度條吸附柱的設(shè)計通常是在已知活性炭的吸附性能、運行負荷和吸附柱高度條件下求吸附所能維持的時

39、間，或者確定吸附時間條件下求吸附柱高度。件下求吸附所能維持的時間，或者確定吸附時間條件下求吸附柱高度。活性炭的活性炭的吸附性能吸附性能設(shè)計指標設(shè)計指標出出水水物物質(zhì)質(zhì)濃濃度度 i b xVbVx累計產(chǎn)水量累計產(chǎn)水量出出水水物物質(zhì)質(zhì)濃濃度度 i b xVbVx累計產(chǎn)水量累計產(chǎn)水量 出出水水物物質(zhì)質(zhì)濃濃度度 i b xVbVx累計產(chǎn)水量累計產(chǎn)水量出出水水物物質(zhì)質(zhì)濃濃度度 i累計產(chǎn)水量累計產(chǎn)水量 吸附能力沒吸附能力沒有得到發(fā)揮有得到發(fā)揮 厚度厚度吸附層吸附層的吸附能力的吸附能力f厚度吸附層的吸附能力出來的吸附能力厚度吸附層中沒有發(fā)揮f%100LfL吸附柱的飽和百分數(shù)(x/m)x(x/m)yy ydy

40、在體積微元內(nèi)，吸在體積微元內(nèi)，吸附量與該時刻該體附量與該時刻該體積微元內(nèi)的有機物積微元內(nèi)的有機物濃度表現(xiàn)平衡關(guān)系，濃度表現(xiàn)平衡關(guān)系，可以用等溫吸附線可以用等溫吸附線來描述來描述在體積微元內(nèi)，單位時間內(nèi)從在體積微元內(nèi)，單位時間內(nèi)從水中去除的有機物的量水中去除的有機物的量=單位單位時間內(nèi)被吸附的有機物的量時間內(nèi)被吸附的有機物的量在體積微元內(nèi)，單位時間內(nèi)從水中去除的有機在體積微元內(nèi)，單位時間內(nèi)從水中去除的有機物的量物的量=單位時間內(nèi)被吸附的有機物的量單位時間內(nèi)被吸附的有機物的量假設(shè)吸附反應(yīng)為一級反應(yīng)，反應(yīng)物有效濃度應(yīng)當為（假設(shè)吸附反應(yīng)為一級反應(yīng)，反應(yīng)物有效濃度應(yīng)當為（ - e）cemkadtd)(t

41、mkaei303. 2lg未知未知通過攪拌吸通過攪拌吸附試驗求附試驗求ka對于單位截面積的體積微元對于單位截面積的體積微元dykadFem)(0到到y(tǒng)積分積分 b到到 積分積分bemdkaFyibemdkaF)()1 (10ydfi e i等溫吸等溫吸附線附線操作線操作線x/m0 e 為求假定單位時間內(nèi)活性炭吸附的有機物量與單位時間內(nèi)通過假定單位時間內(nèi)活性炭吸附的有機物量與單位時間內(nèi)通過單位吸附柱截面面積的有機物量成正比單位吸附柱截面面積的有機物量成正比常數(shù)mxFm/=i時，該直線通過(x/m) i點 - e為吸附為吸附的推動力的推動力Fro the case where the mass t

42、ransfer rate is fast and the mass transfer zone is a sharp wave front, a steady-state balance around a carbon contactor reactor yields:Accumulation = inflow outflow- amount absorbed00eGACeQC tQC tmqQ= volumetric flowrate, L/h;Ce= final equilibrium concentration of absorbate, mg/L;C0= initial concent

43、ration of absorbate, mg/L;qe= adsorbent phase concentration after equilibrium, mg adsorbate/g adsrobentt= time, h;mGAC=mass of absorbent, g;The adsorbent usage rate is defined as GACmQt0eeCCqIf it is assumed that the mass of the adsorbate in the pore space is small compared to the amount adsorbed, t

44、hen the term QCet can be neglected.The adsorbent usage rate is given 0GACemCQtqTo quantify the operational performance of GAC contactor, the following terms have been developed and are used commonly:1. Empty-bed contact time (EBCT)bbfbfVA DDEBCTQv AvEBCT= empty bed contact time, hVb= volume of GAC i

45、n contactor, m3Q= volumetric flowrate, m3/hAb= cross sectional area of GAC filter bed, m2D= length of GAC in contactor, mvf= linear approach velocity, m/h2. Activated carbon densityGACGACbmV GAC= density of GAC, g/LmGAC= mass of GAC, g3. Specific throughput, expressed as m3 of water treated per gram

46、 of carbonSpecific throughput3/bGACGACV tQtmgmEBCTm()bGACbGACV ttEBCTVEBCT4. Carbon usage rate (CUR), expressed as gram of carbon per m3 of water treated5. Volume of water treated for a given EBCT, expressed in liters, Lmassof GAC for givenEBCTLGACusagerate6. Bed life, expressed in days, d3/GACmg mQtCURvolumeof water treated for givenEBCTdQEXAMPLE