Marija Nujić

Arsenic removal by nanoparticles: a review

Contamination of natural waters with arsenic, which is both toxic and carcinogenic, is widespread. Among various technologies that have been employed for arsenic removal from water, such as coagulation, filtration, membrane separation, ion exchange, etc., adsorption offers many advantages including simple and stable operation, easy handling of waste, absence of added reagents, compact facilities, and generally lower operation cost, but the need for technological innovation for water purification is gaining attention worldwide. Nanotechnology is considered to play a crucial role in providing clean and affordable water to meet human demands. This review presents an overview of nanoparticles and nanobased adsorbents and its efficiencies in arsenic removal from water. The paper highlights the application of nanomaterials and their properties, mechanisms, and advantages over conventional adsorbents for arsenic removal from contaminated water.

Influence of mixing on efficiency of coagulation and flocculation process during groundwater treatment from "Jarčevac" water-well

Groundwater is the most important source of drinking water in eastern Croatia and it is characterized with high water hardness and elevated concentrations of iron, manganese, arsenic and natural organic matter which negatively affects aesthetic properties and health safety of drinking water. Drinking water quality standards can be achieved by coagulation and flocculation processes followed by filtration. Efficiency of this method is influenced by chemical and physical properties of raw water, type and dose of coagulant, mixing intensity and mixing time. This study investigated the influence of mixing intensity and mixing time on performance of coagulation and flocculation process for aerated low-turbid groundwater from water-well “Jarčevac”. Influence of mixing was tested using two iron-based coagulants (ferric chloride and ferrous sulfate). Samples were mixed in two sets at constant pH of 7.5 and constant initial total iron concentration. Efficiency of coagulation and flocculation process was determined based on initial and final value of following parameters: amount of natural organic matter, water hardness, alkalinity, concentration of total iron, pH and electrical conductivity. Obtained results showed that ferric chloride is more efficient for treatment of groundwater from “Jarčevac” water-well.Najvažniji izvori vode za pice na podrucju istocne Hrvatske su podzemne vode koje karakterizira visoka tvrdoca i povisene koncentracije željeza, amonija, mangana, arsena i organskih tvari, sto negativno utjece na organolepticka svojstva i zdravstvenu ispravnost vode za pice. Jedan od procesa koji se cesto primjenjuje pri kondicioniranju vode je koagulacija i flokulacija uz naknadnu filtraciju. Na ucinkovitost navedenog procesa utjecu cimbenici poput fizikalno-kemijskih karakteristika sirove vode, doza i vrsta koagulanta te brzina i vrijeme mijesanja u pojedinim fazama navedenog procesa. U ovom radu ispitan je utjecaj brzine i vremena mijesanja koagulanata i vode na ucinkovitost koagulacije i flokulacije pri obradi aerirane podzemne vode vodocrpilista „Jarcevac“ s dva željezova koagulanta – željezov klorid i željezov(II) sufat te je pracen utjecaj brzine i vremena mijesanja na ucinak procesa kroz dva seta, uz pocetnu pH vrijednost vode od 7.5 i pocetnu koncentraciju ukupnog željeza od 4 mg/l. Ucinkovitost je pracena mjerenjem polaznih i zavrsnih vrijednosti kolicine organskih tvari, ukupne tvrdoce, alkaliteta i koncentracije ukupnog željeza te pH vrijednosti i vodljivosti vode. S obzirom na dobivene rezultate moguce je zakljuciti da je ucinkovitija obrada podzemne vode vodocrpilista „Jarcevac“ postignuta pri doziranju željezova klorida.

Toxic Metal Ions in Drinking Water and Effective Removal Using Graphene Oxide Nanocomposite

The discharge of heavy metal ions into the environment, due to extensive industrialization and inadequate waste disposal, has become a worldwide issue. Since heavy metals are not biodegradable, they accumulate in living organisms. The most common toxic metal ions in water are arsenic, lead, copper, cadmium, chromium, nickel, zinc, cobalt and manganese. Different treatment technologies such as coagulation, chemical precipitation, ion-exchange and filtration have been employed for pollutant removal from water, but adsorption is still one of the most suitable technologies for heavy metal ions removal. Recent studies show that graphene oxide, functionalized graphene oxide and their composites can efficiently remove heavy metal ions from water. This chapter reviews the application of graphene oxide nanocomposites in the removal of toxic heavy metal ions from aqueous solution.

Nitrate removal from water by ion exchange

High concentrations of nitrate in water, both in surface and in groundwater, is a consequence of geological composition of soil or human activity. Increased concentrations of nitrate in drinking water is a serious hazard to human health, causing abnormalities such as cancerous growth in human digestion system, while excessive nitrate intake via drinking water can cause methemoglobinemia in infants. Furthermore, the presence of nitrate in aquifers can stimulate eutrophication, which compromise the growth of algae and depletion of dissolved oxygen. Natural and chemical fertilizers in crop production, detergent manufacturing, uncontrolled land discharge of municipal wastewater, and industrial wastes have been identified as the main sources of nitrate in water sources. Nitrate is a stable, highly soluble ion that is difficult to remove by conventional water treatment methods such as coagulation and flocculation. The ion exchange is the most widely used procedure for removing nitrate from water. In this research the possibility of removing nitrate from water was examined by using commercial ion exchangers: Duolite A7 and Relite A490, respectively. The influence of the initial concentration of nitrate (10, 50 and 100 mg/l), the contact time (15 - 1440 min) and the mass of the ion exchanger (0.1 to 0.6 g) was also examined.

NITRATE REMOVAL FROM WATER USING SURFACE-MODIFIED ULTRAFILTRATION MEMBRANES

Elevated nitrate concentrations in natural water sources are a worldwide concern due to the extensive levels of soil N-fertilization. This study investigates three commercially available polyethersulfone (PES) ultrafiltration (UF) membranes with different molecular weight cut-offs (5, 10, and 30 kDa), which we modified with a cationic surfactant, cetylpyridinium chloride to improve their nitrate removal. The nitrate removal efficiency of these membranes was examinated as functions of initial nitrate concentration, pH, and permeate flux. The best nitrate removal efficiency was obtained with a 5 kDa surface-modified UF membrane.