Primena elektrofilterskog pepela modifikovanog kalcijum-hidroksidom i oksidima železa za uklanjanje jona teških metala iz vode

Abstract

Cilj ove disertacije bio je ispitivanje mogućnosti primene modifikovanih oblika elektrofilterskog pepela sa kalcijum-hidroksidom (Ca(OH)2) i oksidima železa za efikasno uklanjanje jona metala iz otpadne vode. U okviru rada sintetizovani su novi adsorpcioni materijali i ispitana je ponovna upotreba iskorišćenog adsorbenta za proizvodnju građevinskog materijala (GM) čime se ostvaruje nova upotrebna vrednost i zaokružuje životni ciklus pepela. Prvi postupak modifikacije pepela (eng. Fly Ash, FA) bio je suvo mešanje sa Ca(OH)2, a drugi siteza u koloni sa železo(II, III)-oksidom (Fe3O4) u obliku magnetita (M) i železo(III)-hidroksidom (α–FeOOH) u obliku getita (G). Dobijeni adsorbenti ispitivani su i označeni kao: FA/Ca(OH)2MFA, FA/MFAM i FA/GFAG. Karakterizacija sirovih uzoraka pepela i dobijenih adsorbenata izvršena je primenom sledećih tehnika: granulometrijska i elementarna analiza, gama spektrometrija (eng. γSpectrometry), tačka nultog naelektrisanja (eng. The Point of Zero Charge, pHpzc), rendgenska difrakciona analiza (eng. XRay Difraction, XRD), metoda adsorpciono/desorpcione izoterme adsorpcije gasa (eng. Brunauer–Emmett–Teller, BET), skenirajuća elektronska mikroskopija (eng. Scanning Electron Microscopy, SEM), infracrvena spektrometrija sa Furijeovom transformacijom (eng. FourierTransform Infrared Spectroscopy, FTIR) i Mosbauerova spektroskopija (eng. Mössbauer Spectroscopy, MS). Ispitana je efikasnost uklanjanja Zn2+, Pb2+ i As(V) primenom MFA i As(V) primenom FAM i FAG adsorbenata. Efikasnost adsorpcije ispitivana je varijacijom mase adsorbenta, temperature, vremena trajanja procesa i pH vrednosti rastvora. Adsorpcija je ispitivana u laboratorijskim uslovima u šaržnom sistemu. Za pripremu adsorbenta za izradu GM adsorpcioni eksperimenti izvedeni su na poluindustrijskom postrojenju. Primenom metode odziva površina određeni su optimalni parametri primenjeni za sintezu adsorbenata i izvođenje adsorpcionih procesa. Maksimalni adsorpcioni kapacitet MFA za uklanjanje jona Zn2+, Pb2+ i As(V), izračunati primenom Lengmirovog (eng. Langmuir) modela, iznosili su 33,13, 26,06 i 29,71 mg g1, redom. ..

The aim of this dissertation is to investigate the utilization of fly ash modified by calcium hydroxide and iron oxides in the efficient removal of metal ions from wastewater. Within this paper, both the effects of new materials on adsorption properties as well as the reuse of the exhausted adsorbent incorporated into construction material (CM) are explored. This, thereby, not only delivers a new usable value of the waste material, but also provides a defined end for the fly ash lifecycle. The first modification process of the fly ash (FA) was to dry mix it with calcium hydroxide. The second was done in a column reactor in order to modify the FA with iron (II, III)oxide (Fe3O4) in the form of a magnetite (M) and iron(III)hydroxide (α–FeOOH) in the form of a goethite (G). The obtained adsorbents were thoroughly investigated and labeled as: FA/Ca(OH)2MFA, FA/MFAM, and FA/GFAG, respectively. The characterization of raw FA and the obtained adsorbents was carried out using the following techniques: granulometric and elemental analysis, gamma spectrometry, point of zero charge (pHpzc), X-ray diffraction (XRD), gas adsorption/desorption isotherms (BET), scanning electron microscopy (SEM), Fouriertransform infrared spectroscopy (FTIR), and Mössbauer spectroscopy (MS). Investigations were carried out for the effective removal of Zn2+, Pb2+ and As (V) using MFA and As(V) removal through the FAM and FAG adsorbents. The adsorption efficiency was tested influencing the adsorbent dose, temperature, time, and pH. The adsorption experiments were carried out under laboratory conditions in a batch system. Further adsorption experiments at a semi-industrial plant were conducted to generate a satisfactory quantity of the adsorbent to be used in the production of CM. The optimal conditions and key parameters for the adsorbents’ synthesis and the performance of the adsorption processes were assessed using the response surface method (RSM). The maximum adsorption capacities of the MFA for Zn2+, Pb2+, and As(V) ions, calculated according to the Langmuir model, were 33.13, 26.06, and 29.71 mg g1, respectively...