Surface and groundwater are often contaminated with toxic anions such as arsenic and selenium. Because of their large surface areas, selenium adsorption on carbon sorbents is considered an attractive water treatment technique. In this present work, selenium sorption on copper-impregnated activated carbon and fly ash-extracted char carbon was evaluated. Unburned carbon was extracted from fly ash using froth floatation techniques, and the carbon sorbents were modified using copper ions. Adsorption experiments confirmed the strong influence of electrostatic forces on equilibrium uptakes of selenite (Se (IV)) and selenate (Se (VI)). Selenium sorption on virgin char carbon was maximum only at acidic pH, i.e., at pH < pHₚzc (pH at point of zero charge). Upon copper modification of the carbon surface, the pHₚzc shifted towards the alkaline region, and as a result, the positive charge density on the carbon surface increased. At pH > pHₚzc, a two- to fourfold increase in sorption coverage and threefold increase in selenium percent removal was observed. Se (IV) sorption was higher compared to Se (VI) sorption. The effect of selenium concentrations and competing anions was studied to evaluate adsorbent performance. The order of maximum surface coverage followed the order: modified char carbon > modified activated carbon > char carbon. The main mechanism of selenium (Se) sorption appeared to be (1) electrostatic attraction of the Se ions to the modified carbon surface at acidic to neutral pH; (2) complexation of Se ions with the copper ions/oxides on the carbon surface; and (3) co-precipitation with copper hydroxides at alkaline pH.

Zero-valent iron has received considerable attention for its potential application in the removal of heavy metals from water. This paper considers the possibility of removal of zinc ions from water by causing precipitates to form on the surface of iron. The chemical states and the atomic concentrations of solids which have formed on the surface of zero-valent iron as well as the type of the deposited polycrystalline substances have been analyzed with the use of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The BET surface area, the pH at point of zero charge (pHPZC), the ORP of the solutions, and the pH and chemical concentrations in the solutions have also been measured. Furthermore, the paper also considers the possibility of release of zinc from the precipitates to demineralised water in changing physicochemical and chemical conditions. In a wide range of pH values, Zn ₓ Fe₃ ₋ ₓ O₄ (where x ≤ 1) was the main compound resulting from the removal of zinc in ionic form from water. In neutral and alkaline conditions, the adsorption occurred as an additional process.

Investigations were undertaken to study sorption of heavy metal ions from aqueous solution onto coal bottom ash. X-ray diffraction analysis of coal bottom ash indicated presence of feldspar (KAlSi₃O₈–NaAlSi₃O₈–CaAl₂Si₂O₈), mullite (Al₆Si₂O₁₃), and magnetite (Fe²⁺Fe³⁺₂O₄). Toxicity characteristics leaching procedure (TCLP) revealed that heavy metal ions such as Fe(II), Fe(III), Mn(II), Cu(II), Zn(II), As(III), As(V), Pb(II), and Cd(II) could be leached out from coal bottom ash. Continuous column test with the bottom ash showed negligible heavy metal ion leach-out at pH 6.0, although at pH 4.2 some heavy metal ion leaching, mainly of Mn(II), was observed. Batch sorption studies with individual heavy metal ions (Fe(II), Cu(II), Zn(II) and Mn(II)) revealed that the heavy metal ion sorption onto coal bottom ash could be described by pseudo-second-order kinetics. Sorption isotherm studies revealed that Langmuir isotherm could adequately describe the heavy metal ion sorption onto coal bottom ash with maximum adsorption capacity (qₘ) ranging from 1.00 to 25.00 mg/g for various heavy metal ions. Removal of heavy metal ions by coal bottom ash is attributed to both adsorption and hydroxide precipitation of heavy metals due to the presence of different oxides (i.e., SiO₂, Al₂O₃, Fe₂O₃, CaO) in coal bottom ash.

The mutagenic and genotoxic activity of vinasses collected from a fuel alcohol plant, located in the municipality of Frontino, Northwestern Colombia, were evaluated. Two samples obtained from an 82-L capacity hybrid reactor (UASB-anaerobic filter (AF)-UASB) were studied under laboratory conditions after being treated with biological oxidation, the first, and the second with Fenton reaction consecutively. Mutagenicity was evaluated in vitro by the Ames test using strains TA98 and TA100 with and without S9 metabolic activation. The genotoxic analysis was conducted using the Allium cepa roots assay where chromosomal aberrations were used as clastogenic or aneugenic response markers, and micronuclei as mutagenic response. The Ames test results showed a strain-dependent positive linear association with the vinasse sample concentration before treatment (dose–response effect). Unlike TA100, strain TA98 showed a mutagenic effect in both the presence and absence of metabolic enzymes. After the biological oxidation treatment, vinasse mutagenicity significantly decreased. Finally, after Fenton treatment, the sample did not induce any mutagenic event. Genotoxic activity was observed in all three samples, but there was a higher frequency in the vinasse sample before treatment. Concerning the frequency of micronuclei, no clear association was observed with either the concentration or the type of sample.

Catalytic ozonation process (COP) is a promising advanced oxidation process for petrochemical wastewater (PCW) treatment. However, the lack of economical and effective catalysts limits its application. Manganese sand ore (MSO) was utilized as a heterogeneous catalyst for ozonation of organic contaminants in PCW in this study. The calcined MSO-assisted COP (cMSO-COP) of aniline exhibited greater degradation than natural MSO-assisted COP or single ozonation process (SOP). The cMSO significantly promoted hydroxyl radical-mediated oxidation, decreased the ozonation activation energy by about 20 %, and doubled the reaction rates in comparison with SOP. The cMSO-COP increased the chemical oxygen demand (COD) removal of PCW twofold relative to SOP. The number of polar organic contaminants decreased by 50 % after cMSO-COP treatment. This study demonstrated the potential use of cMSO for efficient ozonation of petrochemical-derived contaminants at low cost.

In this work, an assessment of groundwater quality and its compliance with Brazilian environmental protection standards was carried out. Ground waters from the Serra Geral aquifer are currently used for human consumption at the western region of the Brazilian state of Paraná. Ground water samples from 10 wells covering the entire Toledo municipality rural region were collected and analysed by two highly accurate and sensitive spectrometric techniques: inductively coupled plasma–optical emission spectrometry (ICP-OES) and total reflection X-ray spectrometry (TXRF). Among all detected elements, 18 elements (As, Ba, Br, Ca, Pb, Cl, Co, Cu, Cr, Fe, P, S, Mn, Ni, K, Ti, V and Zn) were measured by the TXRF technique while three elements (B, Mg and Na) were measured by ICP-OES. Trace element concentration levels were then compared with Brazilian environmental legislation (BEL). From the results obtained, concentrations of chromium, iron, arsenic, selenium, manganese and barium were detectable in some wells at slightly above the maximum limits allowed by the BEL.

The aim of this study was to evaluate the efficiency of a passive point-of-use treatment system, namely, a polyvinyl (alcohol) (PVA) nanofiber membrane/activated carbon column, for the treatment of harvested rainwater. The efficiency of SMI-Q10 [quaternized poly (styrene-co-maleimide)] nanofiber membrane disks placed in a filtration assembly for the treatment of surface water (Plankenburg River, Western Cape, South Africa) and harvested rainwater was also assessed. Two rainwater harvesting tanks were installed at the Welgevallen Experimental farm, Stellenbosch, South Africa, with the filtration system intermittently attached to the tanks for collection of rainwater samples throughout the study period. Parameters used to monitor the filtration systems included heterotrophic bacteria, Escherichia coli, and total coliform enumeration and the presence/absence of adenovirus. When compared to drinking water guidelines, the results indicated that 3 L of potable water could be produced by the synthesized PVA nanofiber membrane/activated carbon column. However, PCR assays indicated that adenovirus and numerous bacteria such as Klebsiella spp., Legionella spp., Pseudomonas spp., and Yersinia spp. were not effectively removed by the filtration system utilized. Additionally, the SMI-Q10 nanofiber membrane disks did not remove viruses from the river or tank water samples as bovine adenovirus 3 strain, simian adenovirus, and human adenovirus A strain were detected in all water samples analyzed. Thus, while the microfiltration system was efficient in reducing the level of indicator organisms to within drinking water standards, further optimization of the electrospun filtration membranes is required as molecular analysis revealed that numerous opportunistic bacterial pathogens and viruses persisted after filtration.

In this study, natural calcium-rich attapulgite (NCAP) was used to develop a low-cost adsorbent for removing fluoride (F⁻) from contaminated water. The results showed that calcination can dramatically increase the F⁻ sorption capacity of NCAP and that the maximum F⁻ sorption capacity occurred at 700 °C. The sorption of F⁻ on NCAP heated at 700 °C (NCAP700) followed pseudo-second-order kinetics and was described by the Langmuir equilibrium model. The estimated F⁻ sorption capacity was approximately 140.0 mg/g at pH 8.0, which was comparable with the sorption capacities of some nanomaterials. The sorption of F⁻ on NCAP700 performed well at pH values of 7 to 10. In addition, anions such as NO₃ ⁻ and SO₄ ²⁻ did not affect fluoride removal, but PO₄ ³⁻ and HCO₃ ⁻ moderately influenced fluoride removal. A column study conducted using NCAP700 with a particle size of 0.2–0.5 mm indicated that the adsorbent could effectively purify nearly 200 bed volumes (BV) of water containing 3.0 mg F/l at pH 8.5. The removal of F⁻ from water mainly resulted from the formation of calcium fluoride precipitates and the complexation of fluoride with the –OH group of NCAP700, which was further confirmed by scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) and X-ray photoelectron spectroscopy (XPS).

The epibenthic amphipod Melita plumulosa shows unique gene expression profiles when exposed to different contaminants. We hypothesized that specific changes in transcript abundance could be used in a battery of quantitative polymerase chain reaction (qPCR) assays as a toxicity identification evaluation (TIE)-like approach to identify the most relevant stressor in field-contaminated sediments. To test this hypothesis, seven candidate transcriptomic markers were selected, and their specificity following metal exposure was confirmed. The performance of these markers across different levels of added metals was verified. The ability of these transcripts to act as markers was tested by exposing amphipods to metal-contaminated field-collected sediments and measuring changes in transcript abundance via qPCR. For two of the three sediments tested, at least some of the transcriptomic patterns matched our predictions, suggesting that they would be effective in helping to identify metal exposure in field sediments. However, following exposure to the third sediment, transcriptomic patterns were unlike our predictions. These results suggest that the seven transcripts may be insufficient to discern individual contaminants from complex mixtures and that microarray or RNA-Seq global gene expression profiles may be more effective for TIE. Changes in transcriptomics based on laboratory exposures to single compounds should be carefully validated before the results are used to analyze mixtures.