1,720,999 research outputs found
Assessment of lake bottom sediment pollution by lead and cadmium
No full textThe aim of the current study is to investigate the relationship between physico-chemical parameters, and to determine levels of certain heavy metals (Pb and Cd) in bottom sediments of Lake Sudotėlis in Lithuania. Organic matter (OM) content and pH were measured. Both positive and negative correlations were detected between the lake bottom sediment content and physical-chemical parameters. The pH of the sediment in all sites was slightly alkaline, e.g. from 7.76±0.02 to 8.21±0.02. Quantity of organic matter in bottom sediments was 10.37±0.30 to 76.50±1.6%. The metals concentrations (in mg/kg of dry weight) ranged 0.42±0.02 to 12.73±0.60 for Pb, and 0.02±0.004 to 6.89±0.33 for Cd
Removal of formaldehyde from synthetic wastewater using natural and modified zeolites
No full textChemically modified and natural zeolite consisting of clinoptilolite and mordenite minerals (Sokirnica Mine, Ukraine) was selected for testing the adsorption ability of formaldehyde. Modified zeolite was produced from natural zeolite by chemical activation with sulphuric acid (H2SO4) 2M at 95-98°C for six hours. Synthetic wastewater was prepared by adding formaldehyde at concentrations equal to or higher than the maximum allowable concentration (MAC) values: 1 MAC = 2 mg/l, 2 MAC = 4 mg/l, 3 MAC = 6 mg/l, 5 MAC = 10 mg/l, and 10 MAC = 20 mg/l. The effects of adsorption time (5 min, 10 min, 30 min, 60 min, 3 h, 5 h, 8 h, and 12 h) were examined for the selected formaldehyde concentrations. Adsorption efficiency, adsorption capacity, and iodine numbers were evaluated for the selected adsorbents. The positive effect of natural zeolite chemical modification was obtained in the range of 5.4 to 24.0%, with an average value of 9.2 %. Iodine number was selected as a parameter for natural zeolite chemical modification with 2M sulphuric acid evaluation. The iodine number before sorption was 154.3 mg∙g-1 and after modificatio
Evaluation of Zinc Accumulation in Moss (Pylaisia polyantha) Growing Near Intensive Traffic Street Based on Modelling and Experimental Data
No full textPylaisia polyantha moss growing near intensive traffic in Geležinis Vilkas street at Vingis Park (Vilnius) was selected as an indicator of environmental pollution. Two models were applied for the study: the Gaussian plume model – for zinc emission from automobiles calculation and mathematical model – for recalculating the zinc emission from transport to zinc concentration in moss. Moss samples were collected during spring, summer and autumn. There were no significant changes in Zn concentrations between these periods. Zn emission dispersion from pollution source was calculated only for one vehicle, in order to reach relationships between environmental conditions and dispersion of Zn emission from vehicle exhaust fumes pipe. It was detected that the concentration of Zn tends to decrease with the distance from the pollution source. It was observed that there was a strong relationship between wind speed and Zn concentration – the slower the wind speed, the higher concentration of zinc in moss
Adsorptive removal of Pb2+ ions from aqueous solutions by peat
No full textPeat has been evaluated as an efficient sorbent. In this paper, peat for removal of Pb 2+ ions from aqueous solution was studied. Peat samples were analyzed for total lead, pH, humidity, and TC (total carbon). Major factors involved, including initial Pb concentration, contact time, and pH, also were investigated. The aqueous solution of lead(II) (0.25 mg/L, 25.0 mg/L, 50.0 mg/L, 75.0 mg/L, and 100.0 mg/L) was agitated at a fixed speed of 20 rpm for 5, 10, 20, 45, 90, 180, and 360 minutes, respectively. At the end of each contact time, the solid was removed by filtration through a 0.45 μm glass filter and then analyzed with an atomic absorption spectrophotometer. Adsorption capacity of peat increases with increasing contact time, initial lead(II) concentration, and was significantly affected by initial pH value in the range from 4.0-7.0. The amount of Pb adsorbed on peat was greatest at pH 6.0, 360 min contact time, and 100 mg/L lead(II) concentration, i.e. 9.489 mg/g. The Freundlich and Langmuir models were used to interpret the sorption behaviour of Pb 2+ ions, and the results showed that the Freundlich model shows a better fitting than the Langmuir model according to correlation coefficients (R 2 >0.98, Freundlich model, R 2 >0.58 Langmuir model)
Experimental investigations of dynamic sorption of diesel from contaminated water
No full textSurface wastewater pollution due to accidental runoff or release of oil or its products is a longstanding and common environmental problem. The aim of the study was to investigate the impact of concentrations of oil products (diesel) and suspended solids, the sorbent type, the water flow rate and the interfering factors (chlorides) on the dynamic sorption of diesel and to test regeneration of polypropylene after its use for sorption. The sorbents used for study included common wheat straw (Triticum aestivum), polypropylene and sorbents modified with hydrogen peroxide solution. Standard methods were used for the determination of the investigated parameters and an in-house procedure employing a gas chromatograph was used for the determination of diesel concentration. The following factors that impact the sorption of diesel were investigated during the study: diesel concentration, concentration of suspended solids; type of sorbent (common wheat straw (Triticum aestivum), wheat straw modified with hydrogen peroxide, and polypropylene), water flow rate; and influence of the interfering factors (chlorides). Filtration speed in the range of investigated speeds does not affect the efficiency of diesel removal. Removal efficiency does not depend on the concentration of diesel before the sorbent reaches its maximum sorption capacity. Filling containing 50% of polypropylene and 50% of wheat straw was used for the study. It was found that polypropylene and wheat straw do not remove chlorides and suspended solids from solution. The study found that the solution of hydrogen peroxide boosts the hydrophobic properties of common wheat straw, but does not affect the sorption of diesel. The recommended number of regenerations of polypropylene should be limited to two
Aplinkos chemija ir vandenų apsauga
No full textLaboratoriniai darbai supažindina su atmosferoje, hidrosferoje bei litosferoje dažniausiai pasitaikančiais cheminiais teršalais ir jų pagrindiniais kokybinio ir kiekybinio nustatymo metodais. Kiekviename darbe pateikiama teorinė dalis, išvardijami naudojami prietaisai ir priemonės, pateikiama darbo atlikimo eiga ir literatūros sąrašas. Leidinys skirtas Vilniaus Gedimino technikos universiteto Aplinkos apsaugos inžinerijos specialybės pagrindinių studijų II ir III kurso, taip pat neakivaizdinių studijų III ir IV kurso studentams, studijuojantiems disciplinas „Aplinkos chemija“ ir „Vandenų apsauga“
Determination of Heavy Metals in Mosses (Pylaisia polyantha) Along the High – Intensive Traffic Flow in Geležinis Vilkas Street (Vilnius, Lithuania)
No full textAtmospheric pollution generated by motor vehicular exhaust has become one of the major reason for scientific
and public concern on a world scale. The area of investigations was situated near the main park of Vilnius
(Vingis park) and Geležinis Vilkas street (Lithuania). The place for the sampling of mosses was chosen according to
the high intensive flow traffic that can cause possible pollution to the atmosphere.
All samples of mosses were taken in this order: 5, 15, 25, 35, 45 meters from the Geležinis Vilkas street. Heavy metals
(HM) were investigated by Atomic Absorption Spectroscopy (AAS), using 210VGP absorption spectrophotometer
at VGTU laboratory. Results of investigation determined, that HM content in samples of Pylaisia polyantha
mosses decreased with a distance from the street. The highest concentrations of HM pollutants were found at the
distance 5 and 15 meters from the Geležinis Vilkas street. Accumulations of HM were found in samples of mosses in
this order: Zn > Cu > Pb > Cr, Ni
The Analysis of Parameters Affecting Indoor Air Pollution and Noise Levels Under the Applied Theory of Covariance Functions
No full textAnalysis variations in the intensity of vectors estimating indoor air pollution (PM2.5, PM10 and CO2) and noise levels are presented. The research was conducted in an office room during COVID-19. The theory of covariance functions was used to analyse changes in the intensity of the vectors of determined parameters. The estimates of the cross-covariance functions of digital vectors and the autocovariance functions of the individual vectors of air pollution and noise recording sensor parameters were calculated in line with the random functions of data arrays measuring the vectors of air pollution sensor parameters. The approximations of covariance functions were calculated by changing the quantisation interval on a time scale and applying software created based on the Matlab procedure package. The stochastic interdependence of the vectors of air pollution and noise level recording sensor parameters and variations in vectors on the time scale was established
Treatment of Water Containing Dyes Using Cellulose Aerogels
No full textIn recent years, there has been an interest in the study of new methods for the removal of dyes from water due to its large-scale use in different industries, for example, for paper printing, textile, leather, pharmaceutical, food or technological applications. It is estimated that more than 700 thousand tons of about 10 000 different types of dyes are produced annually. Most of them are synthetic origin and can generate adverse effects, for example, teratogenic, mutagenic and carcinogenic action. Dyes are mainly applied in the textile industry, and they are usually classified into anionic (acid dyes), cationic (basic dyes) and non-ionic (disperse dyes) dyes. The direct discharge of dyes into the environment can cause various damages to plants and animals: dyes can block the penetration of sunlight, reduce the photosynthetic efficiency of aquatic plants and ultimately destroy the ecological balance of the aquatic ecosystem. This study determined the adsorption efficiency of congo red, methylene blue, rhodamine B and naphthol green B dyes used in textile industry by using the aerogel – an adsorbent synthesized from paper waste. Total carbon was selected as indicator of dye concentration in solution. An increase in fibre content from 3 % to 5 % contributes to the improvement of adsorption properties. The decrease in congo red concentration after an adsorption process was 31.0 % and 38.0 % respectively; the decrease in methylene blue was 2.49 % and 8.15 %; the decrease in naphthol green B was 28.04 % and 34.14 % and the decrease in rhodamine B was 1.28 % and 4.13 %
Numerical modeling of kinetics of heavy metal sorption from polluted water
Full text linkWater protection is one of the most important priorities of environmental protection. It is necessary to reduce pollution of wastewater in order to reduce pollution of drinking‐water and water pools. One of the most dangerous wastewater pollutants are heavy metals (HM). They have a negative influence on people and aquatic water systems. The paper analyses possibilities of the sorption method application for heavy metal elimination from waste‐water. Experimental investigation of HM sorption from water and numerical modeling usage possibilities for prognosis of the HM sorption kinetic process was carried out as well as experimental study of HM elimination efficiency dependence on sorption time of HM from wastewater, when using sorbents. Two pseudo kinetic models, i e the pseudo first‐ and second‐order models, were developed on the basis of experimental investigation. These models were applied in numerical modeling in the computer program PHOENICS. The results of the computer program PHOENICS and those of experimental investigation describing HM sorption from water were compared. After comparing the two pseudo models, it is determined that the pseudo second‐order model suits better for HM sorpti.
Skaitinis sunkiųjų metalų sorbcijos iš užteršto vandens kinetikos modeliavimas
Santrauka
Vandens apsauga yra vienas iš svarbiausių aplinkos apsaugos prioritetų. Norint sumažinti vandens telkinių ir geriamojo vandens taršą, būtina mažinti išleidžiamų nuotekų užterštumą. Vieni iš pavojingiausių nuotekų teršalų – sunkieji metalai, galintys sukelti neigiamą poveikį žmonėms bei vandens ekosistemoms. Straipsnyje nagrinėjama sorbcinio metodo taikymo sunkiesiems metalams šalinti iš nuotekų galimybės, taip pat aprašomi sunkiųjų metalų sorbcijos iš vandens kinetikos tyrimai ir skaitinio modeliavimo taikymas sunkiųjų metalų sorbcijos iš vandens kinetikos proceso prognozei. Atlikti eksperimentiniai sunkiųjų metalų šalinimo iš nuotekų sorbentais efektyvumo priklausomybės nuo laiko tyrimai. Remiantis eksperimentinių tyrimų rezultatais, buvo sudaryti du pseudokinetiniai modeliai – pirmosios eilės ir antrosios eilės. Šie modeliai pritaikyti skaitiniame modeliavime, naudojant kompiuterinę programą PHOENICS. Atliekant skaitinį modeliavimą gauti sunkiųjų metalų sorbcijos iš vandens rezultatai palyginti su eksperimentinių tyrimų rezultatais. Palyginus abiejų pseudomodelių rezultatus nustatyta, kad pseudo- antrosios eilės modelis geriau atspindi sunkiųjų metalų sorbcijos iš vandens kinetiką.
Firstd Published Online: 14 Oct 2010
Reikšminiai žodžiai: sorbcija, sorbentai, sunkieji metalai, pseudokinetiniai modeliai, skaitinis modeliavimas
- …
