The differences in effectiveness of multi-walled carbon nanotubes (MWCNTs) as the dispersive solid-phase extraction (dSPE) sorbent for the selective extraction of polycyclic aromatic hydrocarbons (PAHs) were explained on the basis of theoretical study. It was observed that for low molecular weight PAHs, the recoveries using non-helical and helical MWCNTs were similar. In contrary, for PAHs containing five or more aromatic rings, the extraction efficiency was higher using HMWCNTs than for non-helical ones. Principle component analysis (PCA) as well as providing structural parameters and interaction energies for adsorption processes (PAH + CNT → PAH-CNT) have been used for this purpose. All the PAH + CNT → PAH-CNT adsorption processes considered were found to be thermodynamically favorable. However, the adsorption energies (Eₐdₛ) for PAHs and the helical carbon nanotube surface estimated for the B(a)P-HCNT and I(1,2,3-cd)P-HCNT are substantially less negative than those observed for PAH molecules interacting with the non-helical CNT. Namely, the Eₐdₛ calculated in simulated aqueous environment for the B(a)P-MWCNT(6,2) and I(1,2,3-cd)P-MWCNT(6,2) were respectively − 43.32 and − 59.98 kcal/mol, while values of only − 7.75 kcal/mol (B(a)P-HCNT) and − 9.13 kcal/mol (I(1,2,3-cd)P-HCNT) were found for the corresponding PAH-HCNT systems. Therefore, we conclude that the replacement of MWCNTs with HCNTs leads to PAH-HCNT systems in which the interaction energies are much smaller than those estimated for the corresponding PAH-MWCNT systems. HMWCNTs are therefore recommended as the dSPE sorbent phase for the extraction of both low and high molecular weight PAHs from water samples.

Lead and mercury are two of the most toxic heavy metals in environments. Mesosilicate-templated magnetic nanocarbons with ascorbic acid as carbon precursor were developed through nanocasting processes. The nanocarbon showed effective magnetic separation and the maximum adsorption capacity of 80.6 and 66.3 mg/g for Hg and Pb, respectively. Langmuir model well described adsorption processes of both Hg and Pb from water. Magnetic nanocarbon could be easily separated and incinerated, reducing the volume requiring the disposal. This study indicates that mesosilicate-templated nanocarbons with easy disposal potentials may be good candidates for cleansing Hg and Pb from contaminated water.

Due to water scarcity challenges around the world, it is essential to think about non-conventional water resources to address the increased demand in clean freshwater. Environmental and public health problems may result from insufficient provision of sanitation and wastewater disposal facilities. Because of this, wastewater treatment and recycling methods will be vital to provide sufficient freshwater in the coming decades, since water resources are limited and more than 70% of water are consumed for irrigation purposes. Therefore, the application of treated wastewater for agricultural irrigation has much potential, especially when incorporating the reuse of nutrients like nitrogen and phosphorous, which are essential for plant production. Among the current treatment technologies applied in urban wastewater reuse for irrigation, wetlands were concluded to be the one of the most suitable ones in terms of pollutant removal and have advantages due to both low maintenance costs and required energy. Wetland behavior and efficiency concerning wastewater treatment is mainly linked to macrophyte composition, substrate, hydrology, surface loading rate, influent feeding mode, microorganism availability, and temperature. Constructed wetlands are very effective in removing organics and suspended solids, whereas the removal of nitrogen is relatively low, but could be improved by using a combination of various types of constructed wetlands meeting the irrigation reuse standards. The removal of phosphorus is usually low, unless special media with high sorption capacity are used. Pathogen removal from wetland effluent to meet irrigation reuse standards is a challenge unless supplementary lagoons or hybrid wetland systems are used.

Persistent organic pollutants (POPs) are globally dispersed substances considered to have adverse effects on health and ecosystems. Organochlorine pesticides (OCPs) are POPs. OCPs can be collected from the air by passive samplers using polyurethane foam (PUF). POPs in PUF are generally extracted by Soxhlet, considered as reference extraction method. We offer a different methodology approach to extract 16 OCPs from the PUF. This technology extracts, filters, collects the sample and evaporates the solvent, without sample transfer. It is a modification of the ultrasound-assisted extraction micro-scale cell (M-UAE-MSC) previously patented by our group. A full factorial experimental design (2³ centred) was used to optimise the extraction conditions. The most desirable conditions were 50 °C, 40% ultrasound potency and 20-min extraction time, two extractions. OCP recoveries ranged from 67 to 110%. OCP recoveries were equivalent by M-UAE-MSC and Soxhlet techniques. The method was not suitable for five OCPs, and further refinement is needed. Method linearity (r²) was ≥ 0.98. Limits of detection were observed between 1.2 and 4.6 ng PUF⁻¹, while limits of quantification were found between 3.9 and 15.2 ng PUF⁻¹. The method was applied to determine OCPs collected by PUF passive samplers in Mexico. Endosulfan I was the OCP most frequently observed. The M-UAE-MSC optimised extraction conditions, decreased the extraction time from several hours to less than 1 h and reduced three times the solvent consumption with respect to Soxhlet. This afforded a decrease in the waste generation and a reduction in the OCP-extraction cost up to 80%. The results of this study reveal an efficient and consistent procedure, as well as a simpler, faster, cost-saving and more environmentally friendly method to determine OCPs collected by PUF in passive samplers compared to Soxhlet extraction.

Most drugs are synthesized by human medicine both for the treatment of men and animals and are also produced to maintain their physical and chemical properties for a time sufficient to serve a therapeutic purpose in treatments of some kind of illness. Ciprofloxacin is an antibiotic synthetically obtained in 1987 and belongs to the family of fluoroquinolones and is currently prescribed in certain treatments. This work was developed with the objective of evaluating the adsorption of the ciprofloxacin antibiotic in solution on zinc oxide (ZnO) supported on SBA-15-type mesoporous silica. The results showed that the post-synthesis method is effective in impregnating zinc oxide in SBA-15 and its structure has not been damaged and has not lost its organization in the hexagonal 2D planes. The ZnO-SBA-15 (10%) sample adsorbed 69.10% of ciprofloxacin (25 mg/L) in 180 min. Freundlich adsorption model was observed with the correlation factor of R² = 0.9999, for the adsorbent ZnO-SBA-15 (10%), which showed the best sample. The kinetics was classified as pseudo-second order, as well as the thermodynamic parameters were determined, showing that the process has a spontaneous nature and a value of ΔH° = 4.677 kJ/mol, evidencing that the process has the nature of physiosorption.

Advanced nitrogen-removal onsite wastewater treatment systems (OWTS) are used to reduce total nitrogen (N) levels in domestic wastewater. Maintaining system performance requires regular monitoring and in situ rapid tests can provide an inexpensive option for assessing treatment performance. We used a portable photometer to measure ammonium and nitrate concentrations in final effluent from 46 advanced N-removal OWTS, sampling each site at least three times in 2017. To assess photometer accuracy, we compared measurements made using the photometer with those determined by standard laboratory methods using linear regression analysis and a two-tailed t test to compare regression parameters to those for a perfect linear relationship (slope = 1, intercept = 0). Our results show that photometer-based analysis reliably estimates inorganic N (ammonium and nitrate) concentration in field and laboratory settings. Photometer-based analysis of the sum of inorganic N species also consistently approximated the total N concentration in the final effluent from the systems. A cost-benefit analysis indicated that the photometer is a more cost-effective option than having samples analyzed by commercial environmental testing laboratories after analysis of 8 to 33 samples. A portable photometer can be used to provide reliable, cost-effective measurements of ammonium and nitrate concentrations, and estimates of total N levels in advanced N-removal OWTS effluent. This method can be a viable tool for triaging system performance in the field, helping to identify systems that are not functioning properly and may need to be adjusted or repaired by an operation and maintenance service provider in order to meet treatment standards.

Leachates, particularly those from mature landfills, are difficult to treat by biological processes because of their high toxicity and low biodegradability. Therefore, the development of new treatment technology is necessary. The treatment of landfill leachate by peroxicoagulation and solar peroxicoagulation using a batch electrolytic reactor with a Fe cathode and a Cu anode is proposed. The tested operational variables included pH (2.8 and 8.2), current density (11 and 16 mA cm⁻²), treatment time (5, 10, 15, 20, 25, and 30 min), and presence of solar ultraviolet (UV) light and were collected using a compound parabolic collector. The optimum conditions were a pH, current density, and treatment time of 2.8, 16 mA cm⁻², and 10 min, respectively. The presence of UV did not have a significant effect. The chemical oxygen demand and biochemical oxygen demand removed were 62.3% and 55.5%, respectively. The results of UV-visible absorption, fluorescence, and Fourier transform infrared spectroscopy measurements confirm the oxidation process.

As a result of the destruction of ammunition, mines, and explosive devices by the method of open detonation, the increased concentration of heavy metals is often recorded in the soil of military polygons, which is a serious ecological problem. However, in order to determine the potential risk of such locations to the environment, it is necessary to determine, in addition to the total content, the forms in which the metals are present. In this paper, a sequential extraction method was used to analyze the six fractions of five heavy metals (cadmium, lead, nickel, copper, and zinc) in the soil of the polygon for destruction of ammunition, mines, and explosive devices. Samples were collected from the place of direct detonation (so-called pits) and from the edge of the pit. The aim of this research is determination of metal speciation in order to obtain a better insight in their mobility and risk arising from this. The results showed that heavy metals are predominantly present in the residual, oxide, and organic fractions. Cd and Cu were also significantly present in the mobile fractions due to conducted activities on the polygon. To assess the potential environmental risk of soil, the risk assessment code (RAC) and individual (ICF) and global (GCF) contamination factors were used. According to the RAC, the mobility and bioavailability of the analyzed heavy metals decreases in the following order: Cd > Cu > Zn > Pb > Ni. ICF results show low to moderate risk, while GCF results show low risk in terms of heavy metal contamination in the examined area.

The use of microorganisms for the biodegradation of pollutants is increasingly being studied. But at high concentrations, these pollutants become rather inhibitors for the metabolism of microorganisms. In this study, the biodegradation of ammonium formate at various concentrations (1.59–7.94 mM) by Yarrowia Lipolytica and Pichia guilliermondii isolated from the rubber effluent is studied by following the variation of ammonium ions and formate. A fitting of eight models of substrate inhibition was performed and the parameters were determined by nonlinear regression using MATLAB 8.5 ©. The R² and the RSME allow to choose the best model. The results show that ammonium ions (3.17 mM ammonium formate) are used as substrate; no inhibition is observed. But beyond this concentration, the inhibition effect begins to be observed with the specific rates of ammonium biodegradation which decrease. Formate monitoring reveals that is used as the main source of energy and does not inhibit the growth of yeasts. The models of Luong and Webb seem to be more appropriate for predicting the observed phenomena of inhibition. For Yarrowia lipolytica, R² = 0.958 and 0.998 with RSME = 0.005342 and 0.003433, for Pichia guillermondii, R² = 0.999 and 0.992 with RSME = 0.0005121 and 0.001212.

The release of bisphenols such as bisphenol A (BPA) and its alternative bisphenol S (BPS) into the subsurface environment may cause serious pollutions to soil and groundwater. However, only few works have examined their fate and transport in porous media. In this work, batch and column experiments and mathematical modeling were conducted to study the transport behaviors of BPA and BPS in water-saturated limestone porous media. The effects of contaminant input concentration, solution ion type, and solution ionic strength on the retention and transport of BPA and BPS in the columns were investigated. BPS had higher mobility in limestone porous media than that of BPA. With its input concentration decreased, BPA showed lower mobility, while the transport of BPS in the media was not affected by the input concentration perturbations. The retention of both BPA and BPS was higher in divalent calcium ion solution than that in monovalent sodium solution in limestone porous media. Ionic strength showed little effect on the retention and transport of BPA and BPS except that high concentration of Ca²⁺ inhibited the migration of BPS in the media. Because of its relatively high mobility and toxicity, BPS may present a great risk to groundwater quality and thus may not be an environmentally friendly bisphenol alternative.