Search

Environmental contamination from various industrial sources poses a significant global concern, demanding effective remediation strategies. This study investigates the efficacy of spent coffee grounds-derived carbon material in removing various contaminants, including organophosphate pesticides, pharmaceutical residues, and cationic dyes from aqueous solutions. Adsorption experiments were conducted at different temperatures (25 °C, 30 °C, and 35 °C), and the adsorption behavior was analyzed using various kinetic (pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion) and isotherm models (Freundlich, Langmuir, Temkin, Dubinin-Radushkevich). Our findings reveal a complex adsorption process involving both monolayer and multilayer adsorption on the heterogeneous surface of the material. Temperature significantly influenced adsorption behavior, affecting maximum capacities and interactions. Using a material concentration of 0.5 mg mL−1 increases adsorption capacities for both pesticides, reaching 92.0 mg g−1 for malathion and 259 mg g−1 for chlorpyrifos adsorption. At a material concentration of 0.1 mg mL−1, the carbon material exhibited high adsorption capacities for methylene blue, rhodamine B, amoxicillin, and ceftriaxone, reaching values of 2085 mg g−1, 8250 mg g−1, 82 mg g−1, and 181 mg g−1, respectively. The adsorbent was successfully regenerated using 25 % ethanol solution and reused for at least 10 cycles without significantly impacting the adsorption capacity. These results underscore the potential of spent coffee grounds-derived carbon material as an efficient adsorbent for diverse contaminants, highlighting its promising role in environmental remediation efforts.

The increase of production and consumption persistently introduce different pollutants into the environment. The constant development and improvement of analytical methods for tracking environmental contaminants are essential. The demand for high sample throughput analysis has hit the spotlight for developing selective sensors to avoid time-consuming sample preparation techniques. In addition, the sensor’s sensitivity should satisfy the rigorous demands of harmful compound tracking. Molecularly imprinted plasmonic-based sensors are excellent candidates to overcome selectivity and sensitivity issues. Molecularly imprinted polymers are robust, stable in aqueous and organic solvents, stable at extreme pHs and temperatures, and include a low-cost synthesis procedure. Combined with plasmonic-based techniques, they are the perspective choice for applications in the field of environmental protection. Plasmonic-based sensors offer a lower limit of detection, a broad linearity range, high sensitivity, and high selectivity compared to other detection techniques. This review outlines the optical plasmonic detection of different environmental contaminants with molecularly imprinted polymers as sensing elements. The main focus is on the environmental pollutants affecting human and animal health, such as pesticides, pharmaceuticals, hormones, microorganisms, polycyclic aromatic hydrocarbons, dyes, and metal particles. Although molecularly imprinted plasmonic-based sensors currently have their application mostly in the biomedical field, we are eager to point them out as a highly prospective solution for many environmental problems.

The application of organophosphorus flame retardants (OPFRs) is continuously increasing over the years. There is a growing concern for OPFRs’ safety due to their high production. Unavoidable, large quantities of OPFRs enter the environment. Sewage and solid waste (particularly e-waste) treatment plants are the major sources of OPFRs released into the environment. OPFRs are extensively detected in air, dust, water, soil, sediment, and sludge. This chapter discusses and compares the most advanced analytical procedures of OPFRs, including extraction, purification, gas, and liquid chromatography determination techniques. The environmental occurrence of OPFRs was analyzed. Finally, the accumulation and metabolic pathway of OPFRs on living organisms are overviewed. © 2022 Nova Science Publishers, Inc.

Carbonaceous materials as well as its form functionalized with metallic silver have been prepared by hydrothermal carbonization of fructose. Results are presented to show that nanostructured silver was obtained through the functionalization process. The carbonaceous materials were characterized by: nitrogen adsorption/desorption measurement, XRD, SEM/EDS and FTIR. Samples functionalized with silver were analyzed by: XRD and SEM/EDS. The XRD analysis showed that the carbonaceous materials functionalized with silver by hydrothermal carbonization process were successfully performed. Size of silver particles was found to be approximately 32 nm, indicating formation of nanostructure. All samples were tested as an antimicrobial agent for water disinfection. Presence of nanostructured silver in the sample containing 1 mg/mL carbonaceous materials significantly decreased the number of CFU (dCFU = 97.33 %) if compared to the same sample containing the same amount of carbonaceous materials but without of silver (dCFU 65.33 %).

The Briggs-Rauscher reaction containing malonic acid may undergo a sudden transition from low (state I) to high iodide and iodine (state concentration states after a well-defined and strongly reproducible oscillatory period. This study clearly shows that even though the time-dependent behavior of the oscillatory state is reproducible, the time lag necessary for the appearance of the state I to state II transition after the system leaves the oscillatory state becomes irreproducible for an individual kinetic run. This crazy clock behavior of the state I to state II transition is identified by repeated experiments in which stirring rate is taken as a control parameter and all other parameters such as initial conditions, temperature, vessel surface, and the age of solution were kept constant. Surprisingly, a better stirring condition does not make the transition reproducible; it simply does not allow the transition to happen at all. The proposed mechanism, additional explanations, and proposals for this irreproducibility of state II been presented. Considering the fact that the number of crazy clock reactions is only a few, this study may contribute to a better understanding of fundaments of this phenomenon.

The anodic dissolution of copper electrode in 1 M trifluoroacetic acid (TFA) was investigated by applying linear sweep and cyclic voltammetry. The current-potential (I-E) polarization curves (voltammograms) were interpreted from the perspective of non-linear dynamics. The obtained results showed that the voltammogram can be divided into three separate regions. As the system was moved away from the thermodynamical equilibrium, the first to appear is the region of stable steady-state (marked as SSS1 region). This region was followed by the region of oscillatory states (the OsS region). The SSS1 - GT OsS transition is characterized by bifurcation potential, E (BIF1) = 0.558 V-SCE. The third region, the region of stable steady-state (marked as the SSS2 region) occurs after the OsS - GT SSS2 transition, and is characterized by the potential bifurcation, E (BIF2) = 0.657 V-SCE. The cyclic voltammetry measurement has revealed the lack of hysteresis at the SSS1 a dagger OsS transition, and its existence at the OsS a dagger SSS2 transition (the hysteresis width was 34 mV). The results of this study are presented to demonstrate that the voltammograms of the Cu|1 M TFA oscillating electrochemical system can be considered as a bifurcation diagram, experimentally constructed under dynamical conditions.

Ova doktorska disertacija se bavi potenciodinamičkim ispitivanjem ponašanja struje pri anodnoj polarizaciji bakarne elektrode, u prisistvu 1M CF3COOH (trifluorosirćetna kiselina). Poseban naglasak je dat na ispitivanje strujnih oscilacija koje se generišu u odreĎenoj oblasti potencijala (oscilatorna oblast, oblast OsS). Pojava strujnih oscilacija ukazuje da se elektrohemijski sistem Cu|1M CF3COOH moţe okarakterisati kao strujni elektrohemijski oscilator. Uočena oscilatorna oblast na struja-potencijal polarizacionim krivama se nalazi izmeĎu dve oblasti stabilnih stacionarnih stanja, naime izmeĎu oblasti aktivnog rastvaranja bakarne elektrode (oblast SSS1) i oblasti njene pasivacije (oblast SSS2).Primenom ciklične voltametrije ustanovljeno je da se strujne oscilacije javljaju pri oba smera polarizacije, anodnom i katodnom smeru. Prelaz SSS1OsS karakteriše zanemarljivo mali histerezis (5 mV), dok je širina histerezisa na prelazu OsSSSS2 značajno veća (34 mV). Bifurkaciona analiza je pokazala da se prelaz SSS1OsS odvija preko superkritične Hopfove bifurkacije, dok je prelaz OsSSSS2 okarakterisan homokliničnom bifurkacijom.Tafelova analiza je pokazala da se anodno rastvaranje bakarne elektrode odvija preko mehanizma jednoelektronskog prenosa naelektrisanja. Rendgeno-difrakcionom analizom ustanovljeno je da oksidi bakra (CuO i Cu2O) ne ulaze u sastav pasivnog sloja. Difrakciona refleksija na 2 = 7,95, koja nije mogla biti indeksirana, ulazuje da se u sastavu pasivnog sloja nalazi faza velike elementarne ćelije, najverovatnije so koju čine Cu(I) i/ili Cu(II) trifluoroacetat. Dobijena mikro-porozna struktura površine bakarne elektrode koja je bila izloţena potencijalima unutar oscilatorne oblasti je detektovana primenom mikroskopije atomskih sila, što ukazuje na tačkastu (piting) koroziju.Na osnovu ispitivanja uticaja temperature elektrolitičke ćelije na oscilatorno ponašanje struje, naĎeno je da se unutar temperaturskog intervala 5 – 52 C strujne oscilacije javljaju, This doctoral dissertation deals with potentiodynamic examination of current response during the anodic polarization of copper electrode in the presence of 1M CF3COOH (trifluoroacetic acid). Particular focus is given on investigation of the current oscillations that are generated in certain potential region (oscillatory region, region OsS). Appearance of the current oscillations indicates that the electrochemical system Cu|1M CF3COOH can be classified as a current electrochemical oscillator. The observed oscillatory region at the current-potential polarization curve is situated between two regions of stable steady states, namely between the region of active dissolution of copper electrode (region SSS1) and the region of its passivation (region SSS2).It was determined that the current oscillations occur in anodic and cathodic direction of polarization, by applying of cyclic voltammetry. The transition SSS1OsS is characterized by negligible hysteresis (5 mV), while the width of hysteresis at the transition OsSSSS2 is significantly higher (34 mV). Bifurcation analysis showed that the transition SSS1OsS goes via supercritical Hopf bifurcation, while the transition OsSSSS2 is characterize by homoclinic bifurcation.The Tafel analysis showed that the anodic dissolution of copper electrode immersed in 1M CF3COOH goes via one-electron charge transfer step. X-ray diffraction analysis showed absence of copper oxides (Cu2O and CuO) in passive layer. Diffraction reflections at 2 = 7.95, which could not be indexed, indicates presence of phase with large unit cell in passive layer, most probably salt composed of Cu(I) or/and Cu(II) trifluoroacetate. Obtained micro-porous structure of the copper electrode surface, which was exposed to potentials within oscillatory region was detected by using atomic force microscopy, this indicates a pitting corrosion.Based on the investigation of the temperature effect on current oscillatory behavior, it was found that within temperature int

Ova doktorska disertacija se bavi potenciodinamičkim ispitivanjem ponašanja struje pri anodnoj polarizaciji bakarne elektrode, u prisistvu 1M CF3COOH (trifluorosirćetna kiselina). Poseban naglasak je dat na ispitivanje strujnih oscilacija koje se generišu u odreĎenoj oblasti potencijala (oscilatorna oblast, oblast OsS). Pojava strujnih oscilacija ukazuje da se elektrohemijski sistem Cu|1M CF3COOH moţe okarakterisati kao strujni elektrohemijski oscilator. Uočena oscilatorna oblast na struja-potencijal polarizacionim krivama se nalazi izmeĎu dve oblasti stabilnih stacionarnih stanja, naime izmeĎu oblasti aktivnog rastvaranja bakarne elektrode (oblast SSS1) i oblasti njene pasivacije (oblast SSS2). Primenom ciklične voltametrije ustanovljeno je da se strujne oscilacije javljaju pri oba smera polarizacije, anodnom i katodnom smeru. Prelaz SSS1OsS karakteriše zanemarljivo mali histerezis (5 mV), dok je širina histerezisa na prelazu OsSSSS2 značajno veća (34 mV). Bifurkaciona analiza je pokazala da se prelaz SSS1OsS odvija preko superkritične Hopfove bifurkacije, dok je prelaz OsSSSS2 okarakterisan homokliničnom bifurkacijom. Tafelova analiza je pokazala da se anodno rastvaranje bakarne elektrode odvija preko mehanizma jednoelektronskog prenosa naelektrisanja. Rendgeno-difrakcionom analizom ustanovljeno je da oksidi bakra (CuO i Cu2O) ne ulaze u sastav pasivnog sloja. Difrakciona refleksija na 2 = 7,95, koja nije mogla biti indeksirana, ulazuje da se u sastavu pasivnog sloja nalazi faza velike elementarne ćelije, najverovatnije so koju čine Cu(I) i/ili Cu(II) trifluoroacetat. Dobijena mikro-porozna struktura površine bakarne elektrode koja je bila izloţena potencijalima unutar oscilatorne oblasti je detektovana primenom mikroskopije atomskih sila, što ukazuje na tačkastu (piting) koroziju. Na osnovu ispitivanja uticaja temperature elektrolitičke ćelije na oscilatorno ponašanje struje, naĎeno je da se unutar temperaturskog intervala 5 – 52 C strujne oscilacije javlj, This doctoral dissertation deals with potentiodynamic examination of current response during the anodic polarization of copper electrode in the presence of 1M CF3COOH (trifluoroacetic acid). Particular focus is given on investigation of the current oscillations that are generated in certain potential region (oscillatory region, region OsS). Appearance of the current oscillations indicates that the electrochemical system Cu|1M CF3COOH can be classified as a current electrochemical oscillator. The observed oscillatory region at the current-potential polarization curve is situated between two regions of stable steady states, namely between the region of active dissolution of copper electrode (region SSS1) and the region of its passivation (region SSS2). It was determined that the current oscillations occur in anodic and cathodic direction of polarization, by applying of cyclic voltammetry. The transition SSS1OsS is characterized by negligible hysteresis (5 mV), while the width of hysteresis at the transition OsSSSS2 is significantly higher (34 mV). Bifurcation analysis showed that the transition SSS1OsS goes via supercritical Hopf bifurcation, while the transition OsSSSS2 is characterize by homoclinic bifurcation. The Tafel analysis showed that the anodic dissolution of copper electrode immersed in 1M CF3COOH goes via one-electron charge transfer step. X-ray diffraction analysis showed absence of copper oxides (Cu2O and CuO) in passive layer. Diffraction reflections at 2 = 7.95, which could not be indexed, indicates presence of phase with large unit cell in passive layer, most probably salt composed of Cu(I) or/and Cu(II) trifluoroacetate. Obtained micro-porous structure of the copper electrode surface, which was exposed to potentials within oscillatory region was detected by using atomic force microscopy, this indicates a pitting corrosion. Based on the investigation of the temperature effect on current oscillatory behavior, it was found that within temperature

The influence of hydroxycinnamic acids (HCA) on the oxy-radical generated system, potassium iodide/hydrogen peroxide, was investigated through the enhancement of triiodide (I-3(-)) yield. Caffeic acid, clilorogenic acid, and p-coumaric acid were used as typical representatives of HCA. A linear correlation, with positive slopes, was found between absorption maximum of I-3(-) at 351 urn and HCA concentration in all cases. The magnitude of enhanced I-3(-) production was found to increase in the following order: p-coumaric acid LT chlorogenic acid LT = caffeic acid. A reaction mechanism, which includes negative influence of oxygen-centered free radicals on the I-3(-) yield, was proposed. The enhanced production of I-3(-) by HCA is attributed to their radical scavenging activity. Supported by literature data, results obtained in this study have showed the correlation between radical scavenging activities of HCA and their ability to enhanced I-3(-) generation.

The behavior of chlorogenic acid (CGA) and its interaction with Hg(II), Pb(II), Cu(II), Cd(II) and Zn(II) has been studied using direct current (DC) and differential-pulse polarography (DPP). Adsorptive and kinetic/catalytic anodic waves of CGA have been detected at -0.02 and -0.18 V vs. SCE, respectively; Hg(I)-CGA surface disproportionation has been assumed. Reduction of Hg(II)-ions, added in the buffered solution of CGA (pH 7.5), occurs rather than complexation, while the complex forming ability of CGA towards Pb(II) and Cu(II) has been observed. Stoichiometry 1?:?1 for Pb(II)-CGA, and 1?:?1 and 1?:?2 for Cu(II)-CGA has been established applying Jobs method of continuous variation on DPP data. UV-vis spectrophotometric measurements additionally confirmed the existence and stoichiometry of Cu(II) complexes.

In continuous search for advanced electrocatalytic materials for the hydrogen evolution reaction (HER), based on transition metal series, two types of intermetallic compounds, TiPt and MoPt2, were investigated as cathode materials. Additionally, ionic activator (i.a.), the mixture of Na-molybdate and tris(ethylenediamine)Co(III) chloride, was in situ added into electrolyte, 6 M aqueous potassium hydroxide solution. The objective was to qualitatively compare their electrocatalytic efficiency evaluated by quasi-potentiostatic and galvanostatic technique. Results are presented to show: the Tafel slope, the exchange current density, the overpotential needed for a fixed hydrogen production rate and the apparent energy of activation. Obtained kinetic parameters reveal advanced catalytic ability of the MoPt2 over the TiPt cathode towards HER. Also, important step forward was achieved by using ionic activator. The presence of Mo and Co species attached to the cathode surface was confirmed by XRF analysis. Thus, enhanced catalytic activity was assigned to the formation of Mo-Co-based electrodeposit. Results suggest to significant catalytic performance of the MoPt2 cathode specially if used with ionic activator in alkaline water electrolysis. (c) 2007 Elsevier B.V. All rights reserved.

The aim of this work was to investigate efficiency of the electrolytic separation of hydrogen isotopes (D/H), from alkaline 6 M KOH solution as standard electrolyte, on the Mo-Pt intermetallic phases as cathode materials. We measured the isotope separation factor (alpha) of the single-stage process, as a basic parameter determining the isotope separation efficiency. Furthermore, we have found that some combinations of activating compounds (ionic activators added directly into the electrolyte, assuming in situ activation) can reduce energy needs per mass unit of hydrogen produced, as well as the isotope separation efficiency, compared to those of the standard electrolyte. Also, the electrocatalytic ability of Mo-Pt intermetallic phases for the hydrogen evolution was investigated and evaluated at fixed over-potential (energy input) trough measured current density. Such investigations offer a possibility to optimize the electrolytic process, based on a significant upgrade of the efficiency regarding two needs: hydrogen production and isotope separation. (c) 2007 Elsevier B.V. All rights reserved.

Hydrogen is one of the most widely produced commodities in the world economy. The basic technologies for producing hydrogen via the electrolysis of water have long been known. However, there are disadvantages when using this process. Two-thirds of the operation costs of the electrolyzers are electricity costs. The challenge, addressed.by numerous companies and researchers in the last few years, is the cost cutting by increasing efficiency of the process. The aim of this work was the attempt to optimize the electrolytic hydrogen production from alkaline solution, through the variation of cathode materials and use of ionic activators. The part of our results shows the better electrocatalytic activity of intermetallic phases and the energy consumption is decreased when compared with the industrial data (4.5-5 kWh m(-3) H-2). The role of ionic activator used is also very significant. These results give the opportunity for further research of cumulative effect of the intermetallic electrodes and ionic activators on industrial level. (c) 2005 Elsevier B.V. All rights reserved.