Potencijal primene stabilisanog i „zelenom“ sintezom produkovanog nano gvožđa (0) za remedijaciju sedimenta kontaminiranog metalima

Abstract

Ekološki problem svetskih razmera predstavlja zagađenost sedimenta teškim metalima, usled negativnih ekoloških efekata metala na životnu sredinu. Mnoge zemlje i regioni, kao i naša zemlja suočavaju se sa ovom problematikom, koja je vrlo rasprostranjena usled sve brže urbanizacije i industrijalizacije, a sa sve većom nebrigom usled ispuštanja otpadnih voda bez prethodnog prečišćavanja u vodotokove. Prilikom promene uslova vodenog ekosistema, može doći do izluživanja metala i štetnih efekata na životnu sredinu kao i na zdravlje ljudi. Stoga je remedijacija sedimenata zagađenih metalima ključna aktivnost u okviru procesa potpune sanacije vodenog ekosistema, a ekonomične, efikasne i ekološki prihvatljive tehnike remedijacije su hitno potrebne i rado primenljive u tretmanu na velikoj skali. Pre primene remedijacione tehnike na velikoj skali, neophodna su ispitivanja pri laboratorijskim uslovima i pilot skali. Na kraju svakog uspešnog laboratorijskog ispitivanja nalaze se pilot istraživanja. Pomoću njih se dobija p ravi odgovor u smislu izbora optimalne tehnologije imajući u vidu investicione i operativne troškove, postignuti rezultat i krajnje ciljeve u pogledu upravljanja postrojenjem i otpadom. U ovom radu ispitan je potencijal primene stabilisanog i zelenom sinte zom produkovanog nano Fe(0) zaremedijaciju sedimenta zagađenog teškim metalima. Kao remedijaciona tehnika odabrana je stabilizacija/solidifikacija, koja podrazumeva dodavanje agenasa za imobilizaciju metala u sedimentu sprečavajući time potencijalni rizik od izluživanja metala u životnu sredinu. Konvencionalni materijali poput letećeg pepela, cementa, gline se već odavno koriste u ovu svrhu. Kako u današnje vreme raste potražnja za novim, lako dostupnim agensima za stabilizaciju sedimenta, došlo se na ideju o primeni nanomaterijala na bazi gvožđa, tj. nano Fe(0) stabilisanog nativnom glinom i produkovanog redukcijom pomoću organskih molekula prirodno prisutnih u ekstraktu lišća hrasta i crnog duda. Nanomaterijali su sintetisani i karakterisani različitim metodama i tehnikama. U nastavaku, u cilju efikasnosti njihove primene za stabilizaciju sedimenta, sprovedeni su ekstrakcioni i dinamički laboratorijski testovi izluživanja. Odabrane su smeše sedimenta i nanomaterijala koje su pokazale najbolju efikasnost tr etmana. Nakon toga se ispitivanje nastavilo na pilot skali, gde se pratilo ponašanje nanomaterijala u zavisnosti od konvencionalnih materijala koji su već u literaturi dokumentovani kao efikasni imobilizacioni agensi. Dodatna potvrda uspešnosti tretmana data je analizom i karakterizacijom s/s smeša nakon pilot ispitivanja Na osnovu dobijenih rezultata proces se uspešno pokazao pri laboratorijskim uslovima, a takođe i prilikom pilot tretmana, odnosno nakon pilot tretmana nije došlo do povećanih koncentracija izluživanja metala iz s/s smeša, kao ni degradacije smeša nakon procesa ovlaživanja tokom šest meseci. Na osnovu toga, ovako tertirani sediment se može bezbedno odlagati na deponije, ili pak iskoristiti za „kontrolisanu“ upotrebu, izgradnju puteva,kamenoloma, pomoćnih objekata i slično. Rezultati su doprineli u cilju trajnijeg rešavanja pitanja odlaganja zagađenog (izmuljenog) rečnog sedimenta, pri čemu se u procesu stabilizacije/solidifikacije dobijaju proizvodi sa dodatom vrednošću neumanjenog kvaliteta .Nanomaterijali sintetisani u ovom radu na bazi ekstrakta lišća biljaka doprinose kako očuvanju životne sredine, tako i ekonomičnosti primene remedijacione tehnike. Zahvaljujući velikoj specifičnoj površini, malim dimenzijama čestica i velikom kapacitetu za imobilizaciju teških metala predstavljaju efikasnu alternativu komercijalno dostupnim materijalima, što ih čini veoma atraktivnim i obećavajućim u budućnosti pri tretmanu rečnog sedimenta zagađenog teškim metalima.

The pollution of sediment by heavy metals represents a large environmental problem all over the world. A lot of countries in the region as well as our country deal with this problem, which is widespread because of the fast urbanization and industrialization. There is more and more carelessness about wastewater discharge into water flows without previous purification. When the conditions of the aquatic ecosystem change, metal leaching and harmful effects on the environment and human health can occur. Therefore, remediation of metal-contaminated sediments is crucial activity in the process of the complete ecosystem remediation. Cost effective, efficient and environmentally friendly remediation techniques are urgently needed and readily applicable in large-scale treatment. Before applying remediation techniques on the largescale, both laboratory and pilot tests are necessary. There are pilot studies at the end of each successful laboratory test. Those studies provide the right answer in terms of choosing the optimal technology, taking into account the investment and operating costs, the achieved resultand the ultimate goals in terms of plant and waste management. In this study, the application potential of stabilized and green - synthesized nano Fe(0) for the remediation of heavy metal -contaminated sediment was investigated. Stabilization / solidification technique was chosen as remediation technique which involves the addition of metal immobilizing agents in the sediment thus preventing the potential risk of metal leaching into the environment. Conventional materials such as fly ash, cement and clay have long been used for this purpose. Nowadays there is need for new, easily accessible agents for the sediment stabilization. Therefore it came up with the idea of using iron-based nanomaterials, ie. nano Fe(0) stabilized by native cla y and produced by reduction using organic molecules naturally present in oak and black mulberry leaf extract. Nanomaterials have been synthesized and characterized by different methods and techniques. In order to be effective in their application for sediment stabilization, extraction and dynamic laboratory leaching tests were performed. Mixtures of sediment and nanomaterials were selected that showed the best treatment efficiency. After that, the examination was continued on a pilot scale, where the behavior of nanomaterials was monitored, depending on conventional materials which have already been documented in the literature as effective immobilizing agents.Additional confirmation of treatment success was given by analysis and characterization of s / s mixtures after pilot testing. According to obtained results, the process was successfully demonstrated under laboratory conditions, and also during the pilot treatment. After the pilot treatment there were no increased concentrations of metal leaching from s/s mixtures, nor mixture degradation after the wetting process for six months. Based on that, the sediment treated in this way can be safely disposed of in landfills, or used for "controlled" use, construction of roads, quarries, auxiliary facilities and etc. The results have contributed to the goal of a more permanent solution to the issue of disposal of polluted (slugged) river sediment, whereby in the process of stabilization/solidification, products with added value of undiminished quality are obtained. The nanomaterials synthesized in this paper on the basis of plant leaf extract contribute to both the preservation of the environment and the economy of remediation techniques. Thanks to their large specific surface area, small particle size and large ca pacity for immobilization of heavy metals, they represent an effective alternative to commercially available materials. It makes them very attractive and promising in the future in the treatment of river sediment contaminated with heavy metals.