The removal of arsenic from (ground)-water by adsorbent loaded in polymeric microspheres

Jourmal of Harbin Institute of Technology ( New Series), Vol. 19, No. 1, 2012The removal of arsenic from ( ground) -water by adsorbent loadedin polymeric microspheresFICOLI A ', HOINKIS J', CRISCUOU A', FRANZ C', DE RYCKE M', BLOCKC', DEOWANSA', ISIAM R', DRIOU E 12(1. Intitute on Membrane Technology (ITM-CNR), Via Pietro Bucei, Cubo 17C, 87030 Rende (CS), Italy, a. figoli@ itm. cnr. it;2. Karlshrue University of Applied Sciences, Molukestr. 30 76133 , Karlshrue , Germany; 3. Sustainable Process MaterialsEngineering, GROUP T-Leuven Engineering College, Vesliustraat 13, 3000 Leuven, Belgium)Abstract: Arsenic is a natural tasteless and odourless element, existing in the earth' s crust at average levels ofbetween two and five thousands micrograms per liter ( parts per million). Arsenic is highly toxic to humans，,who are exposed to it primarily from air, food and water. The occurrence of arsenic in groundwater is due to ge-ological composition of soil. High concentrations of arsenic in water are the result of dissolution or desorption offerric oxides and the oxidation of mineral arsenopyrites. Arsenic in drinking water has an important impact onthe human health, especially in the less developed countries. Different methods exist to remove arsenic from aquatic media, and one of them is by adsorption. In this work, the adsorption of both As(II) and As( V) bymeans of novel microspheres has been investigated. In particular, TIO2 has been embedded into polymeric mi-crospheres PES ( PolyEtherSulphone) and PEEK-WC ( PolyEtherEther-Ketone). The main advantages of thisencapsulation adsorption material are: no loss of adsorbents into the water stream, easy to be used and scaled-Key words: arsenic removal, adsorption, TiO2，polymeric microspheresCLC number: X703Document code: AArticle ID: 1005-9113(2012 )010063-04Arsenic poisoning has now become one of the ma-within the European Union 3 and in the USA by thejor environmental worries in some Asian countries, in-EPA [In Bangladesh, the MCL of arsenic in drink-cluding Bangladesh, India, China and Vietnam in A- ing water is still 50 g/L. These new regulations imposesia, where millions of people have been exposed to ex-the development of efficient methods for arsenic removalcessive arsenic through contaminated drinking water.from drinking waters 5. In this context, novel micro-This problem is of global issue today including countriescapsules loaded with different concentration of TiO2in South America, Africa, in the US and also in Eu-( adsorbent) have been produced using a system whichrope to certain extent. Most of arsenic problems in deintegrates the traditional chemical capsule techniqueveloping countries today are caused by natural erosion.( coacervation or phase inversion) and the mechanfcalIn nature arsenic occurs in several chemical formscapsule technique ( pressure extrusion) 6. The micro-as organic or inorganie compounds with different molec- capsules have been characterized by Scanning Electronular sizes and different charges (0, -3, +3 and +5).Microscopy ( SEM ) and Back Scatering ElectronThe prevalent forms in water environments are the inor-( BSE). Furthermore, arsenic removal by means ofganic ones being arsenate ( AsO- ) and/ or arsenitecolumn tests ( containing the microspheres produced )( AsO,3- ). In general, inorganic forms of arsenic anhave been also reported ( Graeme, 1998).nore toxic than organic ones， and trivalent arseniccompounds are characterized by higher toxicity than1 Materials and Methodspentavalent ones ( Graeme, 1998).Long-term intake of arsenic contaminated water ishighly detrimental to humans resulting in severe and1.1 MaterialsThe polymer solvent was N , N-dimethylformamidepermanent impairment of human health. Conse-quently, in recent years, authorities have taken a more( DMF), while the coagulation bath solvents were iso-stringent atitude to arsenic in the environment. Thepropanol ( IPA) and deionized water ( DI). Both DMFand IPA wefrnm Carln Frba Reagents, It-new standard on the maximum contaminant level(MCL) of 10 g/L arsenic in drinking water is recom-aly, and wer中国煤化工_fication. The DImended by the WHOl2J and was recently accepted bothwater was prHCNMHGwatersystem.Received 2011 -11 -20.●63●Journal of Harbin Insiue of Technology (New Series), Vol. 19, No. 1, 2012Adsorbent'Efluent0←Efluent ollection tankFeed pump Feed water tank(a) Toal sphere; (b) Cross section; (c) Zoom (0000x) o the suFig.3 Experimental setup: top-down 间)face of thee micrrosphere; ((d) Zoom.(500x) on the cross section ( outerThe water to be treated was prepared using locallye)ad the nimskepitre ofa PES 50% To.mierophereFig.5 SEM/BSE pictures( without PVP)tap water spiked with the parent solutions of As( I1)and As(v)[8).Experiments on arsenic removal were performedAll experiments were conducted at an Empty Bethby column tests containing the novel polymerice micro-Contact Time ( EBCT) of 3.5 min, and the columnscapsules. In particular, Figs. 6 and 7 show the changewere fed by a peristaltic top-down pump (6). After thein efluent concentration for As(V) and As(II), re-water ( ffluent) was passed through the columns it' sspectively, when the spiked water is treated with PEScollected in an ffluent collection tank. The arsenic in-without PVP and PEEK-WC microspheres both embed-fluent concentration was 500 μg/L at 20 C, and theded with 50 wt% TI02 In Fig. 6, it clearly shows thattests were conducted until the efluent arsenic concen-PEEK-WC microspheres have better adsorption capaci-tration exceeded 10 μg/L. By these tests the maximumties than PES microspheres for the removal of As(V)adsorption capacity of the microspheres, which is inwith750( +52,5 L) versus 250(土17,5 L) treatedcompliance with the 10 μg/L in the efluent recommen-bed volumes till the 10 μg/L (MCL) is reached, re-ded by the WHO standard, was studied.spectively. To improve the adsorption efet of PES thehydrophilie pore former PVP was added, by creating a2 Results and Discussionmore porous structure the inner embedded TiO2 wouldMicrospheres, using both PES and PEEKWC asalso be available.polymer, have been sucessfully produced with andwithout Ti02. As example, SEM and BSE pictures of一PES 50% TiO2- PEEK-WC 50%% TiO3 .PES are shown in Figs.4 and 5. The results show aofwell defined sphericity and an asynmetrie structure ofthe mierospheres produced. In particular, it is visible20a well distribution of TiO2 ( white spots) in the wholemicrosphere structure in Fig. 5. .200600800 1000Bed Volumes TreatedFig.6 As(V) in efluent vs. bed volumes treated at EBCT3.5 min by usingPES without PVP and PEEK-WCmierospheres embedded with TiO2 50% and PESwith PVP embedded with 57% TiO;Fig. 7 shows a similar effect, that PES micro-spheres have a lower adsorption capacity in comparisonwith PEEK-WC microspheres for As (II). At anEBCT of 3,5 min the 10 μg/L (MCL) limit in the ef-fluent for PEEK-WC and PES is reached after 150(土10,5L) and 60( +4,2 L) bed volumes, respec-(a) Total sphere;(b) Cross sction;(e) Zoom (50000x) on the sur-, .noer adsorption offace of the microsphere;(d) Zoom (500x) on the cross secion (outerASs(II) by中国煤化工dvolumes werelayer) of the mierosphereFig.4 SEM/BSE pietures of a PES microsphere( withouthandled theMHC N M H Gstill not reachedPVP)for PEEK-WC," while for PES this guideline wasreached after 550 empty bed volumes.Journal of Harbin Institute of Technology (New Series), Vol. 19, No. 1, 2012reach the TiO2 ( embedded in the polymeric structure).Both types of microspheres allowed to accomplish theES 50% TiO240一PEEK-WC 50% TiO2Bangladesh limit of 50 μg/L in efluent water for both+ PES 57% TiO, with PVPAs(II) and As(V) species.1 20Furthermore, in the proposed system no release ofadsorbent in the purified water stream was observed.三10References :5o0-- 10001500 2000 2500Bed volumes treated[ 1 ] National Research Council. Arsenic in Drinking Water.Fig. 7As(I) in efluent vs. bed volumes treated atWashington, DC: National Academy of Sciences, 2001.EBCT 3.5 min by using PES without PVP and[2] WHO. Guidelines for Drinking Water Quality. TechnicalPEEK-WC microspheres embedded with TiO2Report. Geneva: World Health Organization, 199350%[3] European Comnissin Directive 98/83/EC, Brussels. Relat-ed with drinking water quality intended for human con-PEEK-WC and PES microspheres without adsor-sumption. Brussels, Belgium. 1998.bents were also tested to investigate if there was any[4] US Environmental Protection Agency. Panel 14 : NationalPrimary Drinking W ater Regulations: Arsenic and Clarifi-adsorption by the polymer itself, and no adsorption ca-cations to Compliance and New Source Contaminants Moni-pacity was detected.toring. W ashington DC. 2001 ,66: 194.[5] Uddin M T, Mozumder S I, Figoli A, et al. Arsenie remov-3 Conclusionsal by conventional and membrane technology: an over-view. Indian J of Chem Tech, 2008 ,15:441 - 450.In this work ，polymeric microspheres embedded[6] Figoli A, De Luca G, Longavita E, et al. PEEKWC cap-with TiO2 have been prepared by NIPS and tested forsules prepared by phase inversion technique: a morpholog-arsenic removal from water. The maximum amount ofical and dimensional study. Separation Science and Tech-TiO2 that could be embedded in both PES and PEEK-nology , 2007 ,42(13) :2809 -2827.[7] Smedley P L, Kinniburgh D G. A review of the source, be-WC microspheres was around 50% .haviour and distribution of arsenic in natural waters. Ap-Both As(III) and As(V) were removed from wa-plied Geochemistry , 2002 ,17(5) :517 - 568.ter using the polymeric microspheres prepared with[8] Hoinkis J, Yigitoglu T. Laboratory Sudy on Removal ofPVP additives. The addition of PVP, in fact, allowedArsenic from Drinking W ater by Adsorbing Media. Techni-to prepare a more porous structure which decreases thecal Report. Karlsruhe: Karlsruhe University of AppliedSciences , 2008.mass transfer resistance making easier for the arsenic to中国煤化工MYHCNMHG66●