Characterization and treatment of the phosphoric gypsum transport water.

This paper presents a new treatment procedure applied on phosphogypsum transport water. Untreated transport water is highly acidic (pH 1.79), having fluoride content of 1540 mg/L and elevated values of phosphates (215 mg/L) and heavy metals (Fe=25.8 mg/L; Zn=5.7 mg/L; Mn=2.7 mg/L, V=1.7 mg/L). Neutralization/purification of the transport water was carried out with wood fly ash, otherwise a rich source of calcium, composed of calcite, dipotassium calcium carbonate and hydroxylapatite. Maximum removal efficiency of fluoride was observed at pH 7 (99.99%) and phosphate at pH 9 (96.29%). The removal of fluorides was a consequence of the formation of fluorite and fluorapatite mineral phases derived from the reaction of calcium (released from the fly ash minerals) and fluorides (from the transport water). The removal of phosphates resulted from the formation of fluorapathite and hydroxilapatite. At the optimum conditions removal efficiencies for the elements Pb, V, Cr(VI), Mn, Fe, Ni, Cu, and Zn were 95%, 98.14%, 91.11%, 100%, 99.71%, 96.33%, 97.24%, and 99.65%, respectively. Optimal heavy metal removal occurred in major cases at pH 7.

The assessment of genotoxic effects of wastewater from a fertilizer factory.

In this study we investigated cytotoxic, mutagenic and genotoxic effects of different concentrations of wastewater from the phosphoric gypsum depot near the factory for fertilizing agents 'INA Petrokemija' (Kutina, Croatia). The Ames test was performed on Salmonella typhimurium TA98 and TA100 strains, in the presence of S9 mix, glutathione and buffer, respectively. Cytotoxicity was studied on human laryngeal carcinoma cells (HEp2) and human cervical cells (HeLa). The level of lipid peroxidation in these two cell lines was evaluated in parallel. To establish the levels of primary DNA damage, the alkaline comet assay was performed on treated human peripheral blood leukocytes. No mutagenic effects of phosphoric gypsum on Salmonella typhimurium strains in the presence of S9 mix, GSH or PBS were observed. However, strong cytotoxic effect was observed on both human cell lines when they were treated with different concentrations of wastewater. Lipid peroxidation was induced and increased by prolonged time of incubation, highlighting that the damage was not repaired, but increased with the time of incubation. The results of the alkaline comet assay indicate significant DNA damaging potential of wastewater for human leukocytes. Since phosphoric gypsum transport water in its present composition and acidity is highly toxic and acts as prooxidant, causing free radicals formation and DNA damage, urgent neutralization/purification of the wastewater to a level acceptable for disposal into the environment is mandatory.

Leaching properties of electric arc furnace dust prior/following alkaline extraction.

This study was carried out to determine the appropriate treatment of electric arc furnace (EAF) dust prior to permanent disposal. The total heavy metal content as well as heavy metal leaching from EAF dust was investigated in five composite samples obtained from three Croatian and Slovenian steelworks. In order to recover zinc and reduce its leaching from the dust, all five samples were submitted to alkaline extraction with 10 M NaOH. Reduction of Cr (VI) to Cr(III) was conducted using FeSO4 x 7H2O solution. The elements Mn, Fe, Cu, Ni, and notably Zn and Pb, exhibited highest mobility during toxicity characteristic leaching procedure (TCLP). Comparing to TCLP extracts of initial EAF dust, zinc was found to be over 15 times lower and lead over 200 times lower in TCLP extracts of EAF dust processed by the alkaline leaching method. Since Cr (VI) exceeded its permissible level in the DIN 38414-S4 extracts of both initial and alkaline digested dust, its reduction to Cr (III) prior to permanent disposal is necessary. The recovery of zinc from EAF dust treated with alkaline agent ranged from 50.3% to 73.2%. According to phase analysis, recovery yield showed dependence on zincite/franklinite ratio. The results of the study indicate that permanent disposal of EAF dust require the following procedure: alkaline digestion (followed by leachate purification and alkaline zinc electrolyses), chromate reduction (if necessary), solidification of leaching residue and its testing using the leaching analyses.

Environmental contamination assessment of the surroundings of the ex-ferrochromium smelter Dugi Rat, Croatia.

The objective of this study was to chemically characterize the soil samples affected by the dust emission and slag dumping from ferrochromium smelter, as well as uptake of metals by vegetation growing on that soil. There were 38 samples collected altogether, including unpolluted background soil samples, polluted soil samples taken in the vicinity of the factory, slag material, bottom and fly ash. Grass material was also taken from both polluted and unpolluted soil. All samples were analyzed with energy dispersive X-ray fluorescence (EDXRF). The results showed (especially for chromium and manganese) metal concentrations in soil samples taken in the vicinity of the factory increased up to 56 times in relation to normal background soil concentrations. Slag material, fly and bottom ash were highly enriched with chromium, manganese and nickel. There was a significant chromium uptake by vegetation growing on the contaminated soil.

Chemical and radiological profile of the coal ash landfill in Kastel Gomilica.

The objective of this study was to determine the chemical, radiological and leaching properties of slag and ash produced by a thermoelectric unit of a former factory Adriavinil and deposited in the area of Kasktel Gomilica near Split, Croatia. A total of 33 samples were analysed. The bioavailable fraction of the slag and ash was estimated using different leaching tests. The waste material was characterized by a high activity of naturally occurring radionuclides 238U, 235U and 226Ra and by elevated concentrations of heavy metals. The concentrations of most heavy metals were three to four times as high as in the common soil. Uranium slag and ash concentration was almost 40 times higher than in control soil. More than 37% of the total U could be removed from the slag and ash with the sea water.

Determination of lanthanides by source excited energy dispersive X-ray fluorescence (EDXRF) method after preconcentration with ammonium pyrrolidine dithiocarbamate (APDC).

A new analytical procedure for determination of lanthanides in environmental samples after chemical separation from major matrix elements on DOWEX 50W-X8 resin followed by preconcentration with chelating agent ammonium pyrrolidine dithiocarbamate (APDC) and analyses of thin targets by energy dispersive X-ray fluorescence (EDXRF) method using 109Cd as the source of excitation was presented. Characteristic Lalpha X-ray lines of the lanthanides were used for calculations of the net peak area and mass concentrations. The influence of pH value of the solution and addition of organic matter on the complexation was investigated. Percentage of recovery of each lanthanide after separation on DOWEX 50W-X8 resin was also determined. Accuracy of the method was tested on standard reference materials and real environmental samples (red mud material). For that purpose samples of standard reference materials and red mud were prepared as thick targets and directly analyzed (without the separation step) by EDXRF method using 241Am as the excitation source. In that case lanthanides concentrations were determined over their characteristic Kalpha X-ray lines and results were compared with those obtained after separation/preconcentration step described above. Results showed that selected lanthanides made stable complexes with APDC in the alkaline medium with the maximum recovery at pH=8. The presence of organic matter slightly modified the complexation by means of somewhat higher recovery percentage at pH lower than 7 and approx. 20% lower recovery at pH higher than 7. Recovery of the elements after separation on DOWEX 50W-X8 resin and preconcentration with APDC at pH=8 varied from 91.4% (Pr) to only 24.9% in the case of Dy. Concentrations of lanthanides measured in standard reference material and environmental samples of red mud after microwave digestion, separation on DOWEX 50W-X8 resin, preconcentration with APDC at pH=8 and recalculation on the percentage of recovery were in good agreement with certified values in the case of SRM as well as with the concentrations obtained by direct determination over Kalpha lines using 241Am excitation source in the case of red mud leading to the conclusion that presented method was applicable for the determination of lanthanides in real environmental samples.

Cytotoxicity and mutagenicity study of waste and purified water samples from electroplating industries prepared by use of ferrous sulfate and wood fly ash.

Toxicological safety of the new purification method for electroplating wastewaters (EWW) has been assessed. Method utilizes waste by-product ferrous sulfate and wood fly ash to scavenge heavy metals from EWW. Energy dispersive X-ray fluorescence (EDXRF) analysis of all samples met the law requirements for safe depositing of waste into the environment. The toxicity study consisted of determination of frequency of bacterial and human cell lines survival and the Ames assay (plate incorporation assay and the preincubation assay). Unexpectedly, data obtained indicate cytotoxicity and slight mutagenic potential of purified water. Ames assay showed that combination of alkalis and heavy metals present in the water purified with original fly ash and eluates of fly and waste ash were metabolically activated and conjugated with glutathione, resulting in new metabolites active and toxic for the cell. In order to reduce this effect pretreatment of fly ash (partial removal of highly soluble compounds) are necessary prior to its usage for neutralization /coagulation/flocculation processes.

Heavy metals in the products of deinking flotation of digital offset prints.

This study was undertaken to investigate the suitability of applying the conventional method of chemical deinking flotation of digital offset prints and ecological implications of the disposal of digital offset prints, with special emphasis on the content of heavy metal cations. The EDXRF method was used to determine the concentrations of Pb, Zr, Sr, As, Co, Zn, Cu, Ni, Fe, Mn, Cr, V, Ti, Ca, and K cations in handsheet ashes after flotation as well as in ashes of foams separated from cellulose suspension in the flotation phase. The same method was applied to determine the concentrations of Pb, Cr, Mn, Fe, Ni, Cu, Zn, and Co in process water filtrates obtained from the cellulose suspension after flotation and in foam filtrates. Centrifuging and coagulation previously treated flotation process water, while foam filtrates were centrifuged. Concentrations of Pb, As, Sr, Zr, K, Ca, Ti, V, Cr, Mn, Fe, Cu, and Zn were determined in the sediments obtained by centrifuging process water. The trials were done with unprinted substrates without deinking chemicals, with unprinted substrates in the presence of deinking chemicals and with printed substrates in the presence of deinking chemicals. Cation analysis revealed that deinking chemicals facilitate release of cations from the substrate and their transition into process water. Concentrations of most cations in the flotation process water, in foam water as well as in the sediment of the process water of printed substrate flotation deinking were lower than those obtained by flotation of unprinted substrate suspension. Polymer particles of ElectroInk incompletely separated from cellulose fibers prevent release of cations from cellulose fibers into process water. Deinking chemicals do not affect release of cations from ElectroInk particles, so the substrate is the main source of increased concentration of cations in the water of digital offset print deinking. The major part of cations in process water is bound to the colloid particles of the filler (CaCO3) released by substrate disintegration and to particles of fine fibers.

Purification of electroplating wastewaters utilizing waste by-product ferrous sulfate and wood fly ash.

A new procedure for electroplating wastewater treatment using waste by-product (ferrous-sulfate) and waste (wood fly ash) is presented. Ferrous-sulfate was employed for Cr(VI) reduction whereas neutralization and heavy metal removal from electroplating wastewaters was performed using wood fly ash. Heavy metal removal efficiency varied from 97.5% for Cu to 99.973% for Zn. Satisfying results can be achieved already at the pH 8. The method is suitable for the purposes of wastewater treatment and disposal in compliance with environmental laws. Furthermore, it is technically simple, cost-efficient and requires less space compared to the classical methodology. According to the composition of its water extractable fraction remaining waste ash could be safely deposited on domestic waste repositories.

Environmental contamination assessment of the surroundings of the ex-Sibenik's ferro-manganese smelter, Croatia.

The objective of this study was chemical and radiological characterization of soil samples affected by the dust emission and slag dumping from ferro-manganese smelter as well as uptake of metals by vegetation growing on that soil. Iron was the main component of metallurgical slag deposited near the smelter. Slag material was highly enriched in Zn, Cr, Cu, Co, and Pb. V and Cr were enriched in the soil taken near the smelter approximately by a factor of two, Pb and Cu were increased fivefold whereas the mean content of Mn was about 130 times higher than the levels in background soil samples. Activities of agricultural soil samples were typical for the soil developed on late Cretaceous carbonate surface. 40K, 232Th, and 137Cs showed somewhat lower activities in background soil compared to the soil taken near the smelter while the opposite was found for 226Ra and 238U. Plot of factor 1 against factor 2, obtained by Principal component analysis, showed perfect separation of the samples taken in the vicinity of the smelter, slag material, and normal background agricultural soil. Perfect correlation (Canonical R =0.992) was obtained between chemical composition of soil and vegetation samples taken from the same spots. The content of Mn was approximately 36 times higher in vegetation taken from the vicinity of the smelter compared to the background values.