Istraživanje procesa u koloni s nepomičnim slojem u sustavu prirodni zeolit – vodena otopina olovova i cinkova nitrata

Ispitan je proces uklanjanja olova i cinka postupkom u koloni iz binarnih vodenih otopina ukupnih početnih koncentracija co(Pb+Zn) ≈ 1 mmol/l, a uz mijenjanje omjera co(Pb)/co(Zn) od 0,18 do 2,15. Eksperimenti su provedeni izotermno u staklenim kolonama s nepomičnim slojem prirodnog zeolita klinoptilolita visine 4, 8 i 12 cm. Tijek radnog ciklusa i ciklusa regeneracije pratio se određivanjem koncentracije Pb i Zn iona, te pH vrijednosti u efluentu i regeneratu. Monitoringom pH vrijednosti može se pouzdano i brzo procijeniti točka proboja i završetak regeneracije, što je za praktičnu primjenu od velikog značaja. Rezultati su prikazani krivuljama proboja i krivuljama regeneracije iz kojih su izračunati karakteristični parametri: kapacitet u točki proboja i iscrpljenja, efikasnost uklanjanja, simetrija krivulje proboja, visina zone prijenosa tvari, vrijeme kontakta, količina eluiranih iona, stupanj regeneracije i koncentracijski faktor. Uzastopnim ponavljanjem 12 radnih ciklusa i ciklusa regeneracije postignuto je višestruko iskorištenje zeolita bez smanjenja njegova kapaciteta. Do točke proboja Pb i Zn ioni vežu se istovremeno i razmjerno njihovoj koncentraciji u ulaznoj otopini, a u točki iscrpljenja udio vezanog Pb je veći zbog istiskivanja već vezanih Zn iona Pb ionima iz ulazne otopine. Ovaj je efekt potvrđen regeneracijom zeolita pri kojoj su omjeri količina eluiranih iona nR(Pb)/nR(Zn) značajno veći od Pb/Zn omjera, kao i SEM snimkama čestica zeolita te elementarnom EDS analizom. Regeneracijom zeolita postignuto je potpuno eluiranje iona, a volumeni regenerata su i do 10 puta manji od volumena izvorne otopine. To je od osobitog značaja za primjenu prirodnih zeolita u obradi otpadnih voda. Eksperimentalne krivulje proboja testirane su prema Thomasovu i ADR modelu. Utvrđeno je dobro slaganje eksperimentalnih s modelnim krivuljama proboja, te se dobio uvid u kinetiku i mehanizme prijenosa tvari tijekom procesa izmjene.Removal of lead and zinc from binary aqueous solutions with total initial concentrations co ≈ 1 mmol/l, at different ratios of co(Pb)/co(Zn) from 0,18 to 2,15 has been examined using the column method. Experiments were carried out isothermally in glass columns filled with natural zeolite up to bed depths of 4, 8 and 12 cm. Service and regeneration cycles were studied by monitoring of the Pb and Zn concentrations and pH values in the effluent and regenerate solutions. The measurement of pH values allows efficient determination of the breakthrough point and the end of regeneration. The results are shown by breakthrough curves and regeneration curves and the following characteristic parameters have been calculated: breakthrough and exhaustion capacities, removal efficiency, symmetry of breakthrough curves, height of the mass transfer zone, empty bed contact time, quantity of eluted ions, degree of regeneration, and the concentration factor. Twelve successful service and regeneration cycles were carried out without reducing zeolite capacity. Up to breakthrough, Pb and Zn ions were bound simultaneously according to their concentrations in the influent, while at the exhaustion point the quantity of bound Pb was higher. This is due to the displacement of bound Zn by Pb from the feeding solution. This effect has been confirmed by regeneration of zeolite where the ratio of quantities of eluted ions nR(Pb)/nR(Zn) was much higher than the Pb/Zn ratio in the influent. The displacement effect has also been confirmed by SEM images of zeolite particles and elemental EDS analysis. The regeneration of zeolite provides for complete elution of bound ions and the volumes of regenerates were up to 10 times lower compared to the volume of solutions in service cycles. This contributes to the application of natural zeolites in wastewater treatment processes. The experimentally obtained breakthrough curves have been tested according to the Thomas and the ADR models. The modelled curves showed very good agreement with the experimental ones, and were helpful in estimation of kinetic parameters and mechanisms of mass transfer during the overall process

Removal of carbendazim from aqueous solutions by adsorption on different types of zeolite

Objective: Due to the avid interest in devising economically and environmentally viable and readily available materials for pesticide-contaminated water treatment, the effectiveness of clinoptilolite, a natural zeolite, its modified Na-form, as well as ZSM-5, a synthetic zeolite, was investigated for the removal of the fungicide carbendazim from aqueous solutions. Methods: The removal was investigated using batch adsorption by mixing zeolite and the carbendazim solution at different contact times. At the end of each experiment, the suspensions were filtered, and the residual concentration of carbendazim in the filtrates was measured using high-performance liquid chromatography (HPLC). The experimental results were used to calculate the efficiency of tested zeolite types for the removal of carbendazim from aqueous solutions. Results: Synthetic zeolite was highly effective (94.5%) in removal of carbendazim from aqueous solutions when compared to natural zeolite (19.5–23.3%) and its Na-form (22.5–29.0%). However, the residual carbendazim concentration for all three zeolites tested was above the maximum allowable concentration (MAC). Conclusion: Zeolite ZSM-5 exhibited outstanding properties for the removal of the carbendazim fungicide from aqueous solutions; however, high production costs could be a limiting factor for a wider application in water treatment. For practical applications, natural zeolite may be a more economically viable choice, regardless of its significantly lower removal efficiency. Its surface properties would need to be modified and improved by organic surfactants, which would require additional experiments. Finally, the cost-effectiveness of modified natural zeolite should be compared to the production cost of synthetic zeolite to determine the most effective, economically advantageous, and environmentally friendly solution for the treatment of pesticide-contaminated water

Erratum to: Upgrading fuel potentials of waste biomass via hydrothermal carbonization (Hem. Ind. 75 (5) 297–305 (2021))

This article has been published under the category Technical paper instead of Original scientific paper by mistake made by the Editorial Office of the journal Hemijska industrija during the proofreading process. Apologies are offered to authors and readers of the journal Hemijska industrija.Related to published version: [https://vinar.vin.bg.ac.rs/handle/123456789/10170

Upgrading fuel potentials of waste biomass via hydrothermal carbonization

In recent decades, massive exploitation of fossil fuels caused a growing demand for the production of energies from renewable sources. Hydrochar obtained from waste biomass via hydrothermal carbonization (HTC) possesses good potentials as a biofuel. Therefore, we performed HTC of corn cob, paulownia leaves, and olive pomace at different temperatures (180, 220, and 260oC). The main goal of this study was to comparatively evaluate the influence of HTC conditions on the structure and fuel characteristics of the obtained solids. The results showed that the yields of hydrochar decrease significantly with increasing temperature in all samples. The carbon content and higher heating value increased and reached the highest values in hydrochars obtained at 260°C, while the content of volatile matter decreased. Furthermore, the Van Krevelen diagram reveals that the transformation of feedstock to lignite-like products upon HTC was achieved. In this study, the results showed that processes of dehydration and decarboxylation during HTC provoke intensive biomass transformation and that hydrochars obtained at higher temperatures have significantly enhanced fuel properties and fewer volatiles compared to the feedstock.Link to erratum: [https://vinar.vin.bg.ac.rs/handle/123456789/10171

Evaluation of low-cost sorbents as potential materials for in situ remediation of water contaminated with heavy metals

The aim of this paper was to examine the possibilities of using various low-cost sorbents as material for permeable reactive barrier for efficient removing of lead, cadmium, copper and zinc from contaminated water. Natural zeolite (NZ), iron-modified zeolite (IMZ), apatite, concentrated apatite, kaolin and raw bentonite were examined. The batch test evaluation was used to investigate capturing of heavy metals from contaminated water onto sorbents, as well as retention strength of saturated sorbent. The change of pH values during saturation and leaching of heavy metals was performed in a slightly acidic to neutral area, confirming buffering abilities and environmental acceptability of all investigated sorbents as a material in PRB for protection of groundwater as the most valuable natural resources. The highest saturation ability towards all examined heavy metals was detected with raw bentonite and IMZ. Leaching of heavy metals at pH=2.94-2.98 was confirmed in all saturated sorbents, while at pH=6.07-6.46 it was not detected, except of Pb and Cd in raw bentonite. From the obtaned results, the recommendation for selection of sorbent for treatment of water contaminated with lead, cadmium, cooper and zinc is given

Removal of Ethyl Xanthate Anions from Contaminated Aqueous Solutions Using Hazardous Waste Slag Generated by Lignite Combustion

This paper presents the results of the application of hazardous waste slag generated by lignite combustion for the adsorption of ethyl xanthate anions (EX) from aqueous solutions. The starting material (RWS) was washed (WWS) and modified (MWS) and then characterized in detail by using different chemical and physical–chemical techniques (determination of chemical composition and content of heavy metals, X-ray diffraction (XRD), infrared spectroscopy (FTIR), determination of textural properties and point of zero charge). Besides the chemical stability of EX, the influence of the initial pH, mass of the adsorbent, initial concentration, and time on the EX anion removal was tested. The characterization results showed that applied waste slag is a hazardous material with complex mineral and structural properties but with good buffer properties and pH stability, which is also characteristic of the MWS sample. The adsorption experiments showed that modification with Cu(NO3)2 and Fe(NO3)3 significantly increases the adsorption capacity of the starting slag. Under applied experimental conditions, the maximal adsorbed amount of EX anions on the MWS was 210 mg/g, while equilibrium was obtained after 700 min. The Freundlich model and pseudo-second-order model best fit the results, suggesting the complex mechanism of EX removal by the MWS sample

POLYMYOSITIS AND SYSTEMIC SCLEROSIS OVERLAP – A CASE REPORT AND A REVIEW OF THE LITERATURE

Polimiozitis (PM) autoimunosna je bolest koja primarno zahvaća poprečnoprugastu muskulaturu. U mlađoj životnoj dobi najčešće se radi o idiopatskom obliku povezanom sa specifi čnim autoprotutijelima (anti Jo), dok je u zreloj dobi češće povezana s novotvorinama. PM može biti udružen s drugim autoimunosnim bolestima kao što je sistemska skleroza (SSc), rijetka progresivna bolest kojoj je glavno obilježje patološka fi broza tkiva i organa. 65-godišnji bolesnik, dugogodišnji pušač, primljen je u bolnicu zbog bolnog edema podlaktica i potkoljenica te izražene slabosti proksimalnih mišića udova. Iako mišićni enzimi nisu bili povišeni, dijagnoza PM-a postavljena je na osnovi karakterističnoga patohistološkog nalaza. Na trupu su uočene kožne promjene koje bi mogle odgovarati SSc-u, ali nije bilo pozitivnih autoprotutijela ni drugih dijagnostičkih kriterija SSc-a. Nakon iscrpne obrade zbog moguće maligne bolesti započeta je terapija glukokortikoidima (GK) koja je dovela do jenjavanja edema i jačanja mišićne snage. Već nakon četiri tjedna bolesnik se javlja sa simptomima koji upućuju na SSc: Raynaudov sindrom, disfagija i izrazito zadebljanje kože prethodno otečenih dijelova udova. PM je nerijetko pridružen SSc-u. U ovom slučaju nije jasno je li egzacerbacija latentnog SSc-a potaknuta višim terapijskim dozama GK ili se radi o jednostavnom preklapanju dviju bolesti s različitim početkom. Premda ne postoje terapijske smjernice za liječenje preklapanja PM-a i SSc-a, nužna je oprezna primjena GK već i kod diskretnih naznaka SSc-a zbog poznatog učinka viših doza GK na razvoj i tijek bolesti.Polymyositis (PM) is an autoimmune disease which aff ects skeletal muscles. In young age, it usually occurs as an idiopathic disorder associated with specifi c autoantibodies (anti-Jo), while in older age it is oft en associated with neoplasms. It can present with symptoms of other autoimmune diseases, such as systemic sclerosis (SSc), a rare progresive disease characterized by collagen deposits in various tissues and organs. A 65-year-old patient, long-time smoker, came to the ER because of painful edema in the distal parts of his limbs and proximal muscle weakness of his arms and legs. Although his muscle enzymes were not increased, PM was confi rmed by the characteristic pathohistological fi nding. Th e patient had sclerodermal skin lesions on his back, but he did not have other typical SSc symptoms, and the specifi c autoantibodies were negative. He received glucocorticoid therapy (GC) aft er we had fi nished screening for malignant tumors. He felt better, his muscle strength returned, and the limb edema disappeared. Four weeks later, he developed symptoms which are more typical of SSc, such as dysphagia, Raynaud’s phenomenon, and skin thickening of the limbs that had been swollen. PM is oft en associated with SSc. It is not clear if the exacerbation of latent SSc was stimulated by GC, or if it was just a simple overlap of the two diseases with diff erent onsets. Th ere are no therapy guidelines for the treatment of this combination of diseases. Careful use of GC is necessary even if SSc symptoms are discreet, because of the well-known eff ects of GC in SSc

Ružička days : International conference 16th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: open lecture (1), chemical analysis and synthesis (3), chemical and biochemical engineering (8), food technology and biotechnology (8), medical chemistry and pharmacy (3), environmental protection (11) and meeting of young chemists (2)

Assessment of natural zeolite clinoptilolite for remediation of mercury-contaminated environment

The soil at ancient roasting sites in the surroundings of the Idrija mine (Slovenia) is highly contaminated with mercury. To assess the impact of mercury on groundwater by infiltration and find an eco-friendly remediation method, the leaching of mercury from the soil containing 1347 mg Hg/kg, followed by sorption of the total leached mercury on cost-effective natural zeolite (NZ) clinoptilolite, was performed. The leaching of soil in ultrapure water of pHo = 3.00–11.46 after 24 h resulted in the total leached mercury concentration in the range 0.33–17.43 µg/L. Much higher concentrations (136.9–488.0 µg/L) were determined after the first few hours of leaching and were high above the maximum permissible level in water for human consumption. The NZ showed very good sorption of the total leached mercury, with a maximum removal efficiency of 94.2%. The leaching of mercury in presence of the NZ resulted in a significant decrease of the total leached mercury (1.9–20.3 µg/L compared to 12.8–42.2 µg/L), with removal efficiencies up to 90.5%, indicating immobilization of mercury species. The NZ has a great potential for economically viable remediation of mercury-contaminated environment. However, efforts should be made in the further study of mercury leachability to reduce the mercury concentration in water to acceptable levels

Preparation and characterization of the sulfur-impregnated natural zeolite clinoptilolite for Hg(II) removal fromaqueous solutions

Sulfur-impregnated zeolite has been obtained from the natural zeolite clinoptilolite by chemical modification with Na2S at 150 °C. The purpose of zeolite impregnation was to enhance the sorption of Hg(II) from aqueous solutions. Chemical analysis, acid and basic properties determined by Bohem’s method, chemical behavior at different pHo values, zeta potential, cation-exchange capacity (CEC), specific surface area, X-ray powder diffraction (XRPD), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), as well as thermogravimetry with derivative thermogravimetry (TG-DTG) were used for detailed comparative mineralogical and physico-chemical characterization of natural and sulfur-impregnated zeolites