Lidia Dąbek

A comparative study on oxidative degradation of 2,4-dichlorophenol and 2,4-dichlorophenoxyacetic acid by ammonium persulfate

AbstractThe degradation of 2,4-dichlorophenol (2,4-DCP) and 2,4-dichlorophenoxyacetic acid (2,4-D) by ammonium persulfate under various activation conditions was investigated. The effect of the initial oxidant concentration, pH, temperature, and Fe2+ concentrations were studied. The rate of 2,4-DCP and 2,4-D oxidation was proportional to the concentration of persulfate. The optimal pH for 2,4-DCP degradation was 9.0, while for the 2,4-D, it was 3.0. The effect of temperature on the kinetics of 2,4-DCP and 2,4-D oxidation was examined, and it was demonstrated that increasing the temperature from 25 to 50°C accelerated the oxidation rate of both contaminants. The effects of Fe2+ concentrations and the optimal ratio of persulfate to Fe2+ were studied. Synergistic activation of persulfate by heat and Fe2+ was also investigated to enhance the oxidation of 2,4-DCP and 2,4-D. Under optimal experimental conditions, when the persulfate to Fe2+ molar ratio was 1:2 at 50°C, the complete oxidation of 2,4-DCP and 2,4-...

OXIDATIVE DEGRADATION OF 2-CHLOROPHENOL BY PERSULFATE

The degradation of 2-chlorophenol (2-CP) by persulfate was investigated. The kinetics of persulfate oxidation of 2-chlorophenol in aqueous solutions at various pH, oxidant concentration, temperature, Fe2+ and Cu2+ ions content was studied. Maximum of 2-CP degradation occurred at pH 8. The oxidation rate of 2-CP increased with increasing the persulfate molar excess. The degradation process was significantly influenced by temperature – the higher temperature results in a faster degradation of 2-CP. The activation of persulfate by ferrous and copper ions was also studied. Results showed that persulfate is activated more effectively by iron(II) than copper(II) ions. A comparison of different persulfate activation methods revealed that heat-activation was the most effective. Under optimal conditions, in the presence of ferrous ions at 50 °C, complete degradation of 2-chlorophenol was achieved after about 30 minutes.

Assessing the Influence of the Presence of Heavy Metals Adsorbed on Activated Carbon on the Efficiency of Degradation of Phenol Using Selected Oxidizing Agents

Assessing the Influence of the Presence of Heavy Metals Adsorbed on Activated Carbon on the Efficiency of Degradation of Phenol Using Selected Oxidizing Agents Removing organic substances from wastewater is a complex problem. Different methods are used for this purpose. Recently, much attention has been given to the application of sorption and advanced oxidation processes (AOPs), which contribute also to the regeneration of activated carbon. The analysis presented in this paper focused on determining the influence of Cu(II) and Fe(II) ions adsorbed on activated carbon on the efficiency of oxidation of phenol by means of H2O2, Fentons reagent Fe2+/H2O2 and 1:1 HNO3 solution exposed to 2450 MHz microwaves, and, accordingly, the influence of Cu(II) and Fe(II) ions on the sorptive capacity of regenerated activated carbons. The results show that the chemical regeneration of activated carbon using AOPs resulted in partial oxidation of the adsorbed organic substance. The presence of Cu(II) or Fe(II) ions increased the regeneration efficiency. Using nitric acid to oxidize adsorbed phenol brought about a dramatic decline in the sorptive capacity of activated carbon with respect to this substance and an increase in the sorptive capacity of carbon with respect to metal ions. A serious drawback of this method, however, is that the oxidation of adsorbed phenol caused a significant loss of mass of activated carbon regardless of the oxidizing agent used. Ocena wpływu obecności metali ciężkich zaadsorbowanych na węglu aktywnym na skuteczność degradacji fenolu wybranymi czynnikami utleniającymi Usuwanie zanieczyszczeń organicznych ze ścieków jest złożonym problemem wymagającym stosowania różnych metod. Coraz częściej rozważa się możliwość wykorzystania do tego celu procesu sorpcji i metod pogłębionego utleniania (AOPs), co jednocześnie skutkuje regeneracją węgla aktywnego. W prezentowanej pracy prowadzono badania wpływu zaadsorbowanych na węglu aktywnym jonów Cu(II) i Fe(II) na skuteczność utleniania fenolu z wykorzystaniem H2O2, reakcji Fentona Fe2+/H2O2 oraz roztworu 1:1 HNO3 w obecności mikrofal 2450 MHz, a tym samym wpływu na zdolność sorpcyjną zregenerowanych węgli aktywnych. Wykazano, że chemiczna regeneracja węgla aktywnego z wykorzystaniem metod AOP skutkuje częściowym utlenieniem zaadsorbowanej substancji organicznej. Obecność jonów Cu(II) lub Fe(II) zwiększa skuteczność regeneracji. Wykorzystanie kwasu azotowego do utleniania zaadsorbowanego fenolu skutkuje drastycznym obniżeniem zdolności sorpcyjnych węgla aktywnego względem tej substancji i wzrostem zdolności sorpcyjnych względem jonów metali. Niestety negatywnym skutkiem procesu utleniania zaadsorbowanego fenolu, niezależnie od zastosowanego czynnika utleniającego, jest znaczący ubytek masy węgla aktywnego.

Adsorptive removal of pentachlorophenol from aqueous solutions using powdered eggshell

Abstract The usefulness of untreated powdered eggshell as low-cost adsorbent for the removal of pentachlorophenol (PCP) from aqueous solutions was investigated. The most important parameters affecting the adsorption process, including the pH and ionic strength, were examined. The adsorption characteristics of PCP onto eggshell were evaluated in terms of kinetic and equilibrium parameters. The kinetic data were studied in terms of the pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. The equilibrium data were analyzed using the Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. The pseudo-second order model best described the adsorption kinetics. Using the Langmuir equation, the monolayer adsorption capacity of eggshell for PCP was found to be 0.127 mg/g. The results showed that PCP can be effectively removed from aqueous solution employing eggshell as a cheap adsorbent.

Dynamics of Changes in Microbiological Composition of Stored Sediments

The composition of the sediments formed in the process of stormwater pretreatment is diversified and depends on many parameters, mainly on the quality of stormwater and the land use of the catchment. The stormwater sediments are characterized by heterogeneous chemical and microbiological composition. The aim of this paper was the microbiological evaluation of the sediments from four stormwater catchments in terms of hazard to humans and the environment. The pH, and the content of organic and mineral matter were determined for the examined sediments. The microbiological analysis included the determination of the total number of psychrophilic, mesophilic, and coliform bacteria, including E. coli, and also the number of faecal Enterococci, Salmonella and Shigella. The study was conducted for fresh deposits and those stored for one year in order to determine the dynamics of changes in their biological activity.

The Influence of Pencil Graphite Hardness on Voltammetric Detection of Pentachlorophenol

A pencil graphites were used for detection of pentachlorophenol (PCP) based on differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The voltammetric studies were carried out using a pencil graphite electrode (GPE), carbon paste electrode (CPE) and powdered electrode (PE). The pencil graphites were characterized with scanning electron microscope (SEM), Raman spectroscopy and powder X-ray diffraction (XRD) methods. The effects of deposition potential, scan rate and pulse amplitude were examined to optimize the differential pulse voltammetry conditions. Compared to the other working electrodes the graphite pencil electrodes were recognized by their low cost, simplicity, commercial availability and ease of modification. The voltammetric studies have shown the usefulness of the pencil graphite as an electrode material. Their electrochemical usability increased with decreasing hardness (2B> 5B> 8B).