Analysis and selection of the optimal method of water softening using vikor and ahp method – case study

Prečišćavanje sirove vode do nivoa neophodnog da bi se ona koristila za vodosnabdevanje naselja predstavlja veliki izazov, naročito imajući u vidu da sirova voda nikada nije opterećena samo jednim parametrom zagađenja. Napretkom tehnologija za prečišćavanje vode, posebno membranskih tehnologija, efikasnost tretmana postala je daleko veća. Postavlja se pitanje koja tehnologija je optimalna, u pogledu odstranjivanja štetnih materija, ekonomskih, ekoloških dobiti, itd. U izboru optimalne tehnologije tretmana vode značajnu pomoć mogu da pruže metode višekriterijmske optimizacije. U slučaju koji je razmatran u okviru ovog rada primenjene su metode VIKOR i AHP na izbor optimalne konfiguracije postrojenja za omekšavanje vode bazirane na nanofiltraciji. Metoda VIKOR pokazala je bolji uvid u u fizičke karakteristike parametara i značajniju objektivnost donosioca odluke u odnosu na metodu AHP.Treatment of raw water in order to achieve quality requred for drinking water can be a major challenge, especially considering that raw water usually contains more than one pollutiant. With the advancement of water treatment technologies, especially membrane technologies, the efficiency of water purification has been increasing. The question is which technology is optimal, in terms of removal of pollutants, economic, environmental benefits and other criteria. Methods of multi-criteria optimization can provide significant assistence in choosing the optimal water treatment technology. In this paper, the VIKOR and AHP methods were applied for selection of optimal drinking water treatment scheme of water softening plant based on nanofiltration. The VIKOR method showed a better insight into the physical characteristics of the water quality parameters and a more significant objectivity of the decision maker in relation to the AHP method.[https://www.vodoprivreda.net/wp-content/uploads/2020/12/7-Ognjen-Govedarica-i-saradnici.pdf

Sa vremena analiza potrebnih količina vode za navodnjavanje

Two ways of assessing irrigation water requirements are analyzed in the paper. The relationship between income and outcome water is reconstituted by the water balance equation, and the need for irrigation is determined. Besides of this equation, the needs for irrigation are determined by the CROPWAT model, on the basis of yield decrease of several crops grown on different types of soils. The main components of the water balance equation - effective rainfall and evapotranspiration - are also analyzed, to be used in the calculation of seasonal irrigation requirements.U radu se obrađuje proračun potrebnih količina vode za navodnjavanje. Na osnovu jednačine vodnog bilansa uspostavlja se veza između prihoda i rashoda vode i određuju se potrebe za navodnjavanjem. Osim ove jednačine, u ovom radu se potrebe za navodnjavanjem određuju i pomoću proračuna padova prinosa gajenih useva na različitim vrstama zemljišta. Za ovaj slučaj u radu je primenjen model CROPWAT. U radu je, takođe, prikazan i savremen način određivanja efektivnih padavina i evapotranspiracije, kao glavnih komponenata vodnog bilansa, a u cilju proračuna potrebnih količina vode, tj. norme navodnjavanja

Sa vremena analiza potrebnih količina vode za navodnjavanje

Two ways of assessing irrigation water requirements are analyzed in the paper. The relationship between income and outcome water is reconstituted by the water balance equation, and the need for irrigation is determined. Besides of this equation, the needs for irrigation are determined by the CROPWAT model, on the basis of yield decrease of several crops grown on different types of soils. The main components of the water balance equation - effective rainfall and evapotranspiration - are also analyzed, to be used in the calculation of seasonal irrigation requirements.U radu se obrađuje proračun potrebnih količina vode za navodnjavanje. Na osnovu jednačine vodnog bilansa uspostavlja se veza između prihoda i rashoda vode i određuju se potrebe za navodnjavanjem. Osim ove jednačine, u ovom radu se potrebe za navodnjavanjem određuju i pomoću proračuna padova prinosa gajenih useva na različitim vrstama zemljišta. Za ovaj slučaj u radu je primenjen model CROPWAT. U radu je, takođe, prikazan i savremen način određivanja efektivnih padavina i evapotranspiracije, kao glavnih komponenata vodnog bilansa, a u cilju proračuna potrebnih količina vode, tj. norme navodnjavanja

Functionalization of reduced graphene oxide with redox active molecules via cavitation

Grafen, material z izjemnimi toplotnimi, električnimi, optičnimi in mehanskimi lastnostmi, postaja vse bolj zanimiv za uporabo v sodobnih električnih napravah. S prilagajanjem njegovih lastnosti določenemu namenu, tj. z njegovo funkcionalizacijo, je mogoče izdelati visoko zmogljive elektrodne sisteme. Posebej pomembna je uporaba grafena v Li-organskih baterijskih sistemih, katerih glavni problem je odtapljanje redoks aktivnih molekul v konvencionalnih organskih elektrolitih skozi čas. Grafen ima lahko v teh sistemih dvojno vlogo: 1) izredno porozna, netopna podlaga za vezavo redoks aktivnih molekul, in 2) nosilec naboja. S ciljem odkritja materiala, ki bi zadovoljil naštete kriterije, je bila preučevana možnost funkcionalizacije dveh grafenskih materialov različnih specifičnih površin, z različno vsebnostjo kisikovih skupin, in sicer reduciranega grafen oksida (rGO) ter njegovega prekurzorja, grafen oksida (GO), z izbranimi redoks aktivnimi molekulami (2-aminoantrakinon in antrakinon-2-diazonijev tetrafluorborat) s pomočjo ultrazvočne kavitacije. Z uporabo vrstične elektronske mikroskopije, Brunauer–Emmett–Teller metode, Ramanske spektroskopije, Fourierjeve transformacijske infrardeče spektroskopije in termogravimetrične analize, sklopljene z masno spektrometrijo, je bila izvedena podrobna analiza sintetiziranih materialov. Opažena je bila pomembna prednost pristopa z diazonijevo soljo, kjer je uporaba ultrazvočne kavitacije bistveno prispevala k funkcionalizaciji materialov. Analize so pokazale uspešnost izbranega načina funkcionalizacije, zlasti v primeru GO.Graphene, a material of exceptional thermal, electrical, optical and mechanical properties, is becoming increasingly interesting for applications in modern electrical devices. By adapting its properties to a certain purpose, i.e. by its functionalization, it is possible to make high-capacity electrode systems. Of particular importance is the application of graphene in Li-organic battery systems, whose main problem is the dissolution of redox active molecules in conventional electrolytes over time. Graphene can play a dual role in these systems: 1) extremely porous, insoluble substrate for binding redox active molecules, and 2) charge carrier. In order to find a material that would meet the above criteria, the possibility of functionalization of two graphene materials with different specific surfaces and with different content of oxygen groups, namely reduced graphene oxide (rGO) and its precursor, graphene oxide (GO), with selected redox active molecules (2-aminoanthraquinone and anthraquinone-2-diazonium tetrafluoroborate) by ultrasonic cavitation has been studied. Using scanning electron microscopy, Brunauer–Emmett–Teller method, Raman spectroscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis with mass spectrometry, a detailed analysis of the synthesized materials was performed. A significant advantage of the diazonium salt approach was observed, where the application of ultrasonic cavitation significantly contributed to the functionalization of the materials. The analyses showed the success of the chosen method of functionalization, especially in the case of GO

Mathematical Modelling of Water Quality in Lakes and Reservoirs

U radu je obrađena problematika matematičkog modeliranja ekoloških procesa u jezerima i akumulacijama. Prikazani su principi matematičkog modeliranja najbitnijih fizičkih, hemijskih i bioloških procesa koji utiču na kvalitet vode u jezeru. Izvršena je podela modela kvaliteta vode i prikazan je postupak pripreme ulaznih podataka. Programom WASP4 modeliran je kvalitet vode u akumulaciji Vitman. Ispitivani su efekti smanjenja koncentracije zagađenja u reci Mlavi i njenim pritokama na kvalitet vode u akumulaciji.Mathematical modelling of water quality in lakes and reservoirs is considered. The principles of mathematical modelling of main physical, chemical and biological processes that affect water quality are presented. The classification of water quality models, and process of preparing input data are given. Water quality in reservoir Vitman is simulated by WASP4 modelling program. The effects of reducing pollution concentration in river Mlava and tributaries on water quality in reservoir are examined

Towards improved online dissolution evaluation of Pt-alloy PEMFC electrocatalysts via electrochemical flow cell - ICP-MS setup upgrades

Electrochemical flow cell coupled with an inductively coupled plasma mass spectrometer (EFC-ICP-MS) is a powerful electroanalytical technique to monitor in-situ dissolution of metallic electrocatalysts and to understand mechanism of degradation under operating conditions. Its utilisation has witnessed a notable increase in the electrocatalyst field in the last decade where it has been extensively used to study the stability of platinum group metals (PGMs) under oxygen reduction and oxygen evolution reaction conditions. Online ICP-MS has allowed the scientific and industrial community to optimise the activity and stability of PGMs thanks to a better understanding of the complex metal corrosion processes. Among the different setups, the electrochemical flow cell design is the most common as it is based on a commercially available design. Nonetheless, besides different materials and different electrochemical protocols, the impact of the geometry and various parameters of the setup on the recorded dissolution signal has not been studied until now. Such parameters can influence the results obtained with an EFC-ICP-MS and thus the interpretation of the dissolution mechanism and/or stability assessment. Hereby, we demonstrate that the length of the tubing between the outlet of the cell and the inlet of the ICP-MS impacts the resolution of the PtCo catalyst dissolution peaks. This, in turn, facilitates studies where the detection of extremely low concentrations is necessary, such as under a very narrow potential window. Similarly, a reduced internal volume of the cell restricts Pt redeposition, contributing to a more precise evaluation of stability. These claims were supported by dynamic continuum mechanics modelling of the ion concentration in a model EFC. Finally, we provide guidelines and advice to properly measure dissolution with an electrochemical cell coupled with ICP-MS

Understanding the Crucial Significance of the Temperature and Potential Window on the Stability of Carbon Supported Pt-alloy Nanoparticles as Oxygen Reduction Reaction Electrocatalysts

The present research provides a comprehensive study of carbon-supported intermetallic Pt-alloy electrocatalysts and assesses their stability against metal dissolution in relation to the operating temperature and the potential window using two advanced electrochemical methodologies: (i) the in-house designed high-temperature disk electrode (HT-DE) methodology as well as (ii) a modification of the electrochemical flow cell coupled to an inductively coupled plasma mass spectrometer (EFC-ICP-MS), allowing for highly sensitive time- and potential-resolved measurements of metal dissolution. The findings contradict the generally accepted hypothesis that in contrast to the rate of carbon corrosion, which follows the Arrhenius law and increases exponentially with temperature, the kinetics of Pt and subsequently the less noble metal dissolution are supposed to be for the most part unaffected by temperature. On the contrary, clear evidence is presented that in addition to the importance of the voltage/potential window, the temperature is one of the most critical parameters governing the stability of Pt and thus, in the case of Pt-alloy electrocatalysts also the ability of the nanoparticles (NPs) to retain the less noble metal. Lastly, but also very importantly, results indicate that the rate of Pt redeposition significantly increases with temperature, which has been the main reason why mechanistic interpretation of the temperature-dependent kinetics related to the stability of Pt remained highly speculative until now

Adjusting the operational potential window as a tool for prolonging the durability of carbon-supported Pt-alloy nanoparticles as oxygen reduction reaction electrocatalysts

A current trend in the investigation of state-of-the-art Pt-alloys as proton exchange membrane fuel cell (PEMFC) electrocatalysts is to study their long-term stability as a bottleneck for their full commercialization. Although many parameters have been appropriately addressed, there are still certain issues that must be considered. Here, the stability of an experimental Pt-Co/C electrocatalyst is investigated by high-temperature accelerated degradation tests (HT-ADTs) in a high-temperature disk electrode (HT-DE) setup, allowing the imitation of close-to-real operational conditions in terms of temperature (60 °C). Although the US Department of Energy (DoE) protocol has been chosen as the basis of the study (30,000 trapezoidal wave cycling steps between 0.6 and 0.95 V$_{RHE}$ with a 3 s hold time at both the lower potential limit (LPL) and the upper potential limit (UPL)), this works demonstrates that limiting both the LPL and UPL (from 0.6−0.95 to 0.7−0.85 V$_{RHE}$) can dramatically reduce the degradation rate of state-of-the-art Pt-alloy electrocatalysts. This has been additionally confirmed with the use of an electrochemical flow cell coupled to inductively coupled plasma mass spectrometry (EFC-ICP-MS), which enables real-time monitoring of the dissolution mechanisms of Pt and Co. In line with the HT-DE methodology observations, a dramatic decrease in the total dissolution of Pt and Co has once again been observed upon narrowing the potential window to 0.7−0.85 V$_{RHE}$ rather than 0.6−0.95 V$_{RHE}$. Additionally, the effect of the potential hold time at both LPL and UPL on metal dissolution has also been investigated. The findings demonstrate that the dissolution rate of both metals is proportional to the hold time at UPL regardless of the applied potential window, whereas the hold time at the LPL does not appear to be as detrimental to the stability of metals