Removal of carbamazepine from spiked municipal wastewater using electro-Fenton process.

The electrochemical degradation of carbamazepine (CBZ) in both synthetic solutions (CBZo = 12 mg/L) and enriched municipal effluents (CBZo = 60-70 µg/L) was investigated using an electro-Fenton (EF) process. Different operating parameters were investigated, including current intensity, pH, reaction time, ferrous ion concentration, and the type of anode material. The current intensity, the type of anode material, and the concentration of ferrous ions played an important role in the CBZ degradation efficiency. The degradation was mainly attributed to direct anodic oxidation. The best operating conditions for the synthetic sample were obtained at a current density of 0.2 A, a pH of 3.0, and 120 min of treatment using a boron-doped diamond (BDD) anode in the presence of 0.25 mM of Fe(2+). Under these conditions, 52% of total organic carbon (TOC) and 73% of CBZ were removed. The process was also tested as tertiary treatment for a municipal wastewater treatment plant effluent, and CBZ was completely removed.

Impact of miscanthus cultivation on trace metal availability in contaminated agricultural soils: complementary insights from kinetic extraction and physical fractionation.

In order to assess the impact of in situ energy crop cultivation on Cu, Pb, Zn and Cd availabilities in an area contaminated by atmospheric fallout, a parcel divided in two parts was sampled: one under perennial miscanthus since three years and the other staying under annual crops used as reference. Metal availability parameters determined using EDTA extractions at equilibrium and kinetic extractions were related to metal localization in size fractions after physical fractionation. Extraction at equilibrium as well as kinetically defined labile pools highlighted significantly lower Cu and Pb availabilities in the soil under miscanthus compared to the annual crop reference while physical fractionations highlighted an increased localization of these metals in the fine size fractions. For Zn and Cd, changes in metal availability were highlighted only through the kinetic parameters of extraction rate constants while localization in size fractions changed for Cd only. Indeed for these metals extraction at equilibrium and kinetically defined labile and slowly labile pools failed to show some changes. Organic carbon percentage was significantly higher in the 20-50µm and 200-2000µm fractions for the miscanthus sample underlying the importance of no-tillage and organic carbon inputs. Pearson correlations among metal availability parameters and metal and organic carbon localizations were used to identify the more important fractions involved in the metal availability. Results revealed that available metal pools were related to metal localization in the finer soil fractions (<50µm) and to the organic carbon localization in the 20-50µm and 200-2000µm fractions.

Kinetics as a tool to assess the immobilization of soil trace metals by binding phase amendments for in situ remediation purposes.

Many soil remediation techniques consist in decreasing the mobility of trace metals by means of adding trace metal binding phases. For this study, whose aim is to assess the efficiency of soil remediation method by binding phase amendment, a kinetic fractionation method that provides the labile and slowly labile trace metal amounts in soil has been introduced. Manganese oxides (vernadite) and insolubilized humic acids (IHA) have been used as binding phases for the remediation of four heavily polluted soils. Vernadite amendments are effective for lead and cadmium remediation, whereas IHA amendments are only effective for copper remediation. In most cases, the labile metal fractions decrease dramatically in amended soils (up to 50%); on the other hand, the amounts of total extracted metal near the point of thermodynamic equilibrium often show no significant difference between the amended soil and the control soil. These results highlight the utility of kinetic fractionation in assessing the efficiency of soil remediation techniques and, more generally, in evaluating trace metal mobility in soils and its potential advantages compared to extraction schemes performed under equilibrium conditions. In the future, this kinetic method could be considerably simplified so as to consume much less time allowing its routine use.

Kinetic characterizing of soil trace metal availability using Soil/EDTA/Chelex mixture.

The kinetic aspects are not usually tackled when mimicking the soil trace metal mobilization. In this work, a simple procedure is developed for measuring the kinetics of Pb, Cu and Cd transfer from the soil solid phase towards a resin sink. A ternary system of Soil/EDTA/Chelex was employed for mimicking the metal transfer from two agricultural soil samples into the Chelex. Two different kinetic regimes (P(1) and P(2)) were observed. The kinetic profile of Pb was distinctly different from those of Cd and Cu. Basing on kinetic principles, two kinetic models were proposed for estimating the apparent rate constants of leaching and removal processes in, respectively, two binary mixtures of soil/EDTA and EDTA extracts/Chelex. Contrary to Pb, solid phase pools of Cd and Cu exchanged with the solution on short time scales. The kinetic rate of desorption occurred in following order: Pb

Application of advanced oxidation processes for TNT removal: A review.

Nowadays, there are increasingly stringent regulations requiring drastic treatment of 2,4,6-trinitrotoluene (TNT) contaminated waters to generate treated waters which could be easily reused or released into the environment without any harmful effects. TNT is among the most highly suspected explosive compounds that interfere with groundwater system due to its high toxicity and low biodegradability. The present work is an overview of the literature on TNT removal from polluted waters and soils and, more particularly, its treatability by advanced oxidation processes (AOPs). Among the remediation technologies, AOPs constitute a promising technology for the treatment of wastewaters containing non-easily biodegradable organic compounds. Data concerning the degradation of TNT reported during the period 1990-2009 are evaluated in this review. Among the AOPs, the following techniques are successively debated: processes based on hydrogen peroxide (H(2)O(2)+UV, Fenton, photo-Fenton and Fenton-like processes), photocatalysis, processes based on ozone (O(3), O(3)+UV) and electrochemical processes. Kinetic constants related to TNT degradation and the different mechanistic degradation pathways are discussed. Possible future treatment strategies, such as, coupling AOP with biological treatment is also considered as a mean to improve TNT remediation efficiency and kinetic.

Kinetic extractions to assess mobilization of Zn, Pb, Cu, and Cd in a metal-contaminated soil: EDTA vs. citrate.

Kinetic EDTA and citrate extractions were used to mimic metal mobilization in a soil contaminated by metallurgical fallout. Modeling of metal removal rates vs. time distinguished two metal pools: readily labile (QM1) and less labile (QM2). In citrate extractions, total extractability (QM1+QM2) of Zn and Cd was proportionally higher than for Pb and Cu. Proportions of Pb and Cu extracted with EDTA were three times higher than when using citrate. We observed similar QM1/QM2 ratios for Zn and Cu regardless of the extractant, suggesting comparable binding energies to soil constituents. However, for Pb and Cd, more heterogeneous binding energies were hypothesized to explain different kinetic extraction behaviors. Proportions of citrate-labile metals were found consistent with their short-term, in-situ mobility assessed in the studied soil, i.e., metal amount released in the soil solution or extracted by cultivated plants. Kinetic EDTA extractions were hypothesized to be more predictive for long-term metal migration with depth.

Kinetic approach to heavy metal mobilization assessment in sediments: choose of kinetic equations and models to achieve maximum information.

Studies of trace metal mobilization in sediments are generally performed using sequential extraction schemes at equilibrium. In the present work, a kinetic fractionation of trace metals in sediments has been developed to assess that information. The extraction rate data have been obtained using a single extraction scheme with EDTA and following a protocol previously optimized. Two kinetic equations and two kinetic models were used to fit the experimental data. The two constants equation fits well the extraction rate data used in this work but does not present any physico-chemical meaning. The diffusion model and the two first-order reactions model allow determining which parameter (the reaction between the metal M and the EDTA or the diffusion of the complex M/EDTA) is rate limiting in the trace metal extraction by EDTA. It appears that the two first-order reactions model is more efficient than the diffusion model to fit the present extraction rate data so it can be deduced that the diffusion of the complex M/EDTA is not the limiting step of the trace metal extraction by EDTA in estuarine sediments. In a second part, relationships between the fraction of metals determined with the two first-order reactions model and the sediments composition were established.

Rapid determination of polycyclic aromatic hydrocarbons in sewage sludges using microwave-assisted solvent extraction. Comparison with other extraction methods.

The presence of toxic organic micropollutants in municipal sewage sludges is a major problem on account of risks associated with the agricultural use of the sludges and therefore maximum tolerance limits are imposed. The aim of our study was to develop a reliable and fast analytical procedure for the determination of polycyclic aromatic hydrocarbons in sewage sludges, using focused microwave-assisted extraction. Optimization of the extraction conditions was performed on real matrices. The results of a 2(3) factorial design showed that extraction time was the only influential factor. The selected conditions (30 W, 10 min, 30 ml solvent) were used for real sludges and a certified marine sediment, leading to recoveries of between 56 and 75%. Results of an interlaboratory test confirmed these values. Finally, the technique was compared to traditional techniques (Soxhlet, sonication), and the more recent pressurized liquid extraction technique. Focused microwave-assisted extraction remains an attractive alternative technique due to its rapidity, the low solvent volume required and its moderate investment cost.