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Wpływ pola ultradźwiękowego na adsorpcję kationów kadmu

Lach J., Okoniewska E., Stępniak L., Ociepa E.

Rocznik Ochrona Środowiska

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2013

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Tom 15, cz. 3

2142--2157

EN

Adsorption on activated carbon is one of the methods applied for removal of heavy metals from water and wastewater contaminated with these elements. Ion exchange is a predominating mechanism in the process of sorption of ions. In case of sorption of heavy metals cations various surface aggregates are formed. Other processes, such as reduction and oxidation, and precipitation in the pores of insoluble compounds (e.g. hydroxides, carbonates) also occur. The processes behind the formation of aggregates with various degrees of resistance have a particular effect on the selectivity of ion exchange on activated carbons. The chemical composition of activated carbon surface – in particular, the presence of oxygen groups capable of ion exchange – shows the most significant effect during adsorption of heavy metals ions. Typically, the surface of the activated carbons produced with the steam-gaseous method has functional groups both of acidic and alkaline character that are capable of exchanging cations as well as anions. Carbon materials with no functional groups can also sorb protons. This is possible due to the fact that dislocated electrons π in the solutions act as Lewis base. There are a number of methods currently being investigated that would allow for improving the efficiency of adsorption of heavy metals. In the presented work the effect of ultrasonic field on the adsorption of cadmium from the model solutions was analyzed. Various configurations of ultrasonic field applied in the process of adsorption were investigated. Ultrasounds were generated in the UP 400S disintegrator. In the first phase the activated carbon in the form of granules was modified with the ultrasonic field of acoustic power density of 42,5 W/cm2or 85,0 W/cm2, at the amplitude of 30 and 60 µm, and at the exposure time of 5, 10, 15 and 20 min. Modified activated carbons were used for sorption of cadmium ions from the solutions at the initial concentrations ranging from 2,24 do 11,2 mg/dm3. The adsorption of cadmium on the activated carbon modified with ultrasounds (at the amplitude of 30 µm and 60 µm) and at the shortest exposure time (i.e. 5 min.) was higher than on the initial activated carbon. The most favorable results were obtained for the activated carbon modified with ultrasonic field with the acoustic power density of 42,5 W/cm3 and the exposure time of 10 min. The efficiency of cadmium adsorption for the highest concentration increased from 50% (the initial activated carbon) to 63%. Also, the work included the analysis of the effect of ultrasonic field on the cadmium solution with the activated carbon in the form of granules in the first phase of static adsorption. In this case, no significant differences in the adsorption capacities were observed. Also, the effect of ultrasounds on the solution used for the adsorption of cadmium did not have an impact on the efficiency of adsorption. In the final phase of the investigations the effect of sonification on the adsorption of cadmium on the powdery activated carbon was analyzed. The control sample was mechanically mixed for 5 min, and the remaining samples were subjected to the ultrasonic field at various amplitudes but with the same exposure time. The efficiency of adsorption combined with ultrasounds was significantly higher. The final concentrations during the adsorption without ultrasounds were in the range of 0,291 to 1,778 mg/dm3 whereas for the adsorption combined with ultrasounds these concentrations ranged from 0,13 to 0,748 mg/dm3.

2

Tiksotropia osadów powstających w galwanizerni

Soboniak E., Bień B.

Inżynieria i Ochrona Środowiska

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2006

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T. 9, nr 3

287-299

PL

Przeprowadzono ocenę właściwości tiksotropowych osadów na podstawie wyznaczonej doświadczalnie pętli histerezy. Do badań zastosowano przemysłowe osady ściekowe pochodzące z galwanizerni, zlokalizowanej na terenie zakładu zajmującego się nakładaniem powłok galwanicznych. Osady kondycjonowano wstępnie polem ultradźwiękowym przez 5 sekund, stosując amplitudy 8, 12, 16 μm, a następnie dodawano polielektrolitu Praestol 2515. Dawki polielektrolitu dobrano na podstawie testu CSK. Oceny badanych układów dokonano w przedziale zmian prędkości deformacji 0 ÷ 100 s-1 w czasie 228 s oraz w zakresie 100 ÷ 0 s-1 w czasie 114 s i temperaturach: 15, 20, 25°C. Na podstawie przeprowadzonych pomiarów otrzymano zbiory punktów wyznaczających krzywe płynięcia, które nie pokrywały się, dając pętle histerezy. Przeprowadzono również obliczenia powierzchni pętli histerezy oraz wskaźnika tiksotropii. Na podstawie uzyskanych wyników stwierdzono, że istnieje wpływ temperatury oraz amplitudy drgań na wartość wskaźnika tiksotropii. Przedstawione wyniki badań właściwości tiksotropowych przemysłowych osadów ściekowych są dowodem na niestabilność struktury badanych osadów.

EN

The paper presents the results of research concerning the impact of industrial sewage sludge conditioning on changes of rheological parameters. The sludge was choosen from a galvanizing plant. Preliminary, the samples were sonicated for 5 seconds using three different amplitudes 8, 12, 16 μm (the field of 22 kHz was used) and next, polyelectrolytes were used for sludge conditioning anionic polyelectrolyte Praestol 2515. Based on the CST test the optimum doses of polyelectrolyte were determined and added to sludge prior to rheological measurements. The experiment was performed at three temperatures 15, 20, 25°C. The rheological tests were carried out at the shear rate from 0 to 100 s-1 during 228 s and from 100 to 0 s-1 during 114 s. Basing on the histeresis loop the thixotropic coefficients were calculated, and the relationships between them and the temperature. The change of temperature influences on the thixotropic properties of the sludge structure. Thixotropic coefficients show that the structure of industrial sludge is not stabile. Therefore rheological properties are a useful tool in sludge characterization as it allows to determine the stability of structure and the resistance to shearing stresses during sludge conditioning.

3

Badanie zmian niektórych własności osadów ściekowych w procesie kondycjonowania polem ultradźwiękowym

Bień J. B., Wolny L.

Inżynieria i Ochrona Środowiska

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2000

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T. 3, nr 1/2

11-16

PL

Przedstawiono fragment badań dotyczący sposobu preparowania osadów ściekowych przed odwadnianiem. Pole ultradźwiękowe zostało zastosowane jako czynnik modyfikujący działanie polielektrolitów. Ta fizyczna metoda kondycjonowania osadów nie stanowi zagrożenia dla środowiska. Określono charakterystykę osadów odwadnianych w procesie filtrowania, po ich preparowaniu polielektrolitami modyfikowanymi. Podjęto próbę porównania uzyskanych efektów dla ich dawek optymalnych i nadźwiękawianych.

EN

In the paper the part of investigations concering the way of sewage sludges preparation before dewatering was presented. Ultrasonic field was used as an agent of polyelectrolytes modification. This physical method of sludges conditioning is not hazardous to the environment. The characteristics of dewatered sludges in the filtration process was determined after their preparation with polyelectrolytes as well as with polyelectrolytes after modification. The attempt was made to compare the results obtained for optimal doses of sonicated polyelectrolytes.