Study of the effect of pH, salinity and DOC on fluorescence of synthetic mixtures of freshwater and marine salts

In order to provide support for the discussion of the fate of organic matter in estuaries, a laboratory simulation was performed by changing freshwater ionic strength, pH and organic matter content. The change in spectroscopic characteristics caused by variations in salinity, pH and organic matter concentration in the filtered samples was observed by UV-Vis and fluorescence spectroscopy. The increase in emission fluorescence intensity of dissolved organic matter (DOM) due to increasing salinity (in the range 0 to 5 g l−1) is affected by the pH of the samples. The emission fluorescence intensity at the three maxima observed in the fluorescence spectra, is linearly correlated with dissolved organic carbon (DOC) concentration at several salinity values in the same sample. The increase in organic matter concentration caused a shift in the emission peak wavelength at 410 nm for several salinity values.We concluded that it is necessary to take into account the influence of salinity and pH on emission fluorescence of dissolved organic matter if it is to be used as a tracer in estuarine or near shore areas

Stacking effect via solvent polarity differences in micellar electrokinetic chromatography with aqueous-organic background electrolyte

In this manuscript, a new stacking mode for micellar electrokinetic chromatography with anionic micelles and neutral analytes was investigated. The variation in the velocity of the analytes between the sample and the separation zones, needed for stacking effects, was obtained by using solvents with different polarities, the concentration of salts and micelles being identical between the two zones. Whereas a pure aqueous solvent was used in the injection zone, up to 30% ACN was used in the separation zone. In such conditions, higher interactions between the analyte and the micelles are obtained in the sample zone than in the separation zone, this due to the presence of the organic solvent. As the velocity of neutral analyte depends on its interactions with the moving micelles, its speed will drop when crossing two distinct zones where in the second zone its interactions with the micelles are lower than in the outgoing zone. This will induce a stacking effect. This approach was validated using a background electrolyte in the separation zone made with 10 mM disodium hydrogen phosphate, 15 mM sodium dodecyl sulphate and 15% ACN. The three triazines (simazine, atrazine, and terbuthylazine), used as test analytes, were dissolved in 10 mM disodium hydrogen phosphate, 15 mM sodium dodecyl sulphate and either 15 or 0% ACN. A stacking factor of around 2 was obtained injecting the sample in 0% ACN rather than 15% ACN. This was in accordance with the theoretical values predicted measuring the effective mobilities in both zonesCOMPETE/QREN/UE and PTDC/QUI-QUI/116156/2009 and SFRH / BPD / 30548 / 200

Adsorption of pharmaceuticals from biologically treated municipal wastewater using paper mill sludge-based activated carbon

A waste-based alternative activated carbon (AAC) was produced from paper mill sludge under optimized conditions. Aiming its application in tertiary wastewater treatment, AAC was used for the removal of carbamazepine, sulfamethoxazole, and paroxetine from biologically treated municipal wastewater. Kinetic and equilibrium adsorption experiments were run under batch operation conditions. For comparison purposes, they were also performed in ultrapure water and using a high-performance commercial AC (CAC). Adsorption kinetics was fast for the three pharmaceuticals and similar onto AAC and CAC in either wastewater or ultrapure water. However, matrix effects were observed in the equilibrium results, being more remarkable for AAC. These effects were evidenced by Langmuir maximum adsorption capacities (qm, mg g-1): for AAC, the lowest and highest qm were 194 ± 10 (SMX) and 287 ± 9 (PAR), in ultrapure water, and 47 ± 1 (SMX) and 407 ± 14 (PAR), in wastewater, while for CAC, the lowest and highest qm were 118 ± 7 (SMX) and 190 ± 16 (PAR) in ultrapure water and 123 ± 5 (SMX) and 160 ± 7 (CBZ) in wastewater. It was found that the matrix pH played a key role in these differences by controlling the surface electrostatic interactions between pharmaceutical and AC. Overall, it was evidenced the need of adsorption results in real matrices and demonstrated that AAC is a promising option to be implemented in tertiary wastewater treatments for pharmaceuticals' removal. Graphical abstract Production of an alternative activated carbon (AC) comparing favourably with a commercial AC in the removal of neutral and positive pharmaceuticals from wastewater.publishe

Obtaining granular activated carbon from paper mill sludge: a challenge for application in the removal of pharmaceuticals from wastewater

In this work, a granular activated carbon (GAC) was produced using primary paper mill sludge (PS) as raw material and ammonium lignosulfonate (AL) as binder agent. PS is a residue from the pulp and paper industry and AL is a by-product of the cellulose pulp manufacture and the proposed production scheme contributes for their valorisation together with important savings in GAC precursors. The produced GAC (named PSA-PA) and a commercially available GAC (GACN), used as reference material, were physically and chemically characterized. Then, these materials were tested in batch experiments for the adsorption of carbamazepine (CBZ), sulfamethoxazole (SMX), and paroxetine (PAR) from ultra-pure water and wastewater. Even though GACN and PSA-PA possess very similar specific surface areas (SBET) (629 and 671 m2 g-1, respectively), PSA-PA displayed lower maximum adsorption capacities (qm) than GACN for the pharmaceuticals here studied (6 ± 1-44 ± 5 mg g-1 and 49 ± 6-106 ± 40 mg g-1, respectively). This may be related to the comparatively higher incidence of mesopores in GACN, which might have positively influenced its adsorptive performance. Moreover, the highest hydrophobic character and degree of aromaticity of GACN could also have contributed to its adsorption capacity. On the other hand, the performance of both GACs was significantly affected by the matrix in the case of CBZ and SMX, with lower qm in wastewater than in ultra-pure water. However, the adsorption of PAR was not affected by the matrix. Electrostatic interactions and pH effects might also have influenced the adsorption of the pharmaceutical compounds in wastewater.publishe

Fixed-bed performance of a waste-derived granular activated carbon for the removal of micropollutants from municipal wastewater

This work aimed to assess the fixed-bed adsorptive performance of a primary paper mill sludge-based granular activated carbon (PSA-PA) for the removal of pharmaceuticals, namely carbamazepine (CBZ), sulfamethoxazole (SMX) and paroxetine (PAR), from water. The breakthrough curves corresponding to the adsorption of CBZ at different flow rates and in two different matrices (distilled and urban wastewater) were firstly determined, which allowed to select the most favorable flow rate for the subsequent experiments. The fixed-bed adsorption of CBZ, SMX and PAR from single and ternary solutions in wastewater showed that the performance of PSA-PA was different for each pharmaceutical. According to the obtained breakthrough curves, the poorest bed adsorption capacity, either from single or ternary solution, was that for SMX, which may be related with electrostatic repulsion at the pH of the wastewater used (pH ~ 7.3–7.7). Also, the bed adsorption capacity of PSA-PA for SMX was notoriously lower in the ternary than in the single solution, while it slightly decreased for CBZ and even increased for PAR. The regeneration studies showed that the CBZ adsorption capacity of the PSA-PA bed decreased about 38 and 71% after the first and the second thermal regeneration stages, respectively. This decline was comparatively larger than the corresponding reduction of the PSA-PA specific surface area (SBET), which decreased only 5 and 25% for the first and second regeneration, respectively, and pointed to the lack of viability of more than one regeneration stage.publishe

Kinetics of Eucalypt Lignosulfonate Oxidation to Aromatic Aldehydes by Oxygen in Alkaline Medium

The oxidation kinetics of lignosulfonates (LS) from acidic magnesium-based sulfite pulping of Eucalyptus globulus wood with oxygen under alkaline conditions was studied. The analysis of oxidation products in the reaction system O(2)/NaOH revealed a predominance of aromatic aldehydes (vanillin and syringic aldehyde) though small amounts of vanillic and syringic acids and acetophenone/phenylacetaldehyde derivatives have also been detected. The rate constant of syringic aldehyde formation was roughly twice of that for vanillin. The effective activation energies for the oxidation of LS to aromatic aldehydes (ca. 60-70 kJ/mol) were rather different to those found for the formation of aromatic acids (ca. 110 kJ/mol) indicating different mechanisms involved in the rate-determining reaction step. The addition of catalyst (copper salt, 20% w/w) promoted the LS oxidation with increments of aromatic aldehyde yields by 25-50%. The maximum yields of syringic aldehyde and vanillin upon LS oxidation were 16.1 and 4.5%, respectively (150 degrees C, 20 min, P(O2) = 10 bar, 0.9 M NaOH solution). The highly negative effect of concomitant sugars in sulfite liquor to the yield of aromatic aldehydes was highlighted

Photodegradation of sulfamethoxazole in environmental samples: the role of pH, organic matter and salinity

Sulfamethoxazole (SMX) is the most representative antibiotic of the sulfonamides group used in both human and veterinary medicine, and thus frequently detected in water resources. This has caused special concern due to the pronounced toxicity and potential to foster bacterial resistance of this drug. Therefore, and to further understand the fate of SMX in the aquatic environment, its photodegradation under simulated solar radiation was here studied in ultrapure water and in different environmental samples, namely estuarine water, freshwater and wastewater. SMX underwent very fast photodegradation in ultrapure water, presenting a half-life time (t1/2) of 0.86 h. However, in environmental samples, the SMX photodegradation rate was much slower, with 5.4 h < t1/2 < 7.8 h. The main novelty of this work was to prove that pH, salinity and dissolved organic matter are determinant factors in the decrease of the SMX photodegradation rate observed in environmental samples and, thus, they will influence the SMX fate and persistence, potentially increasing the risks associated to the presence of this pollutant in the environment.publishe

Core-shell molecularly imprinted polymers on magnetic yeast for the removal of sulfamethoxazole from water

In this work, magnetic yeast (MY) was produced through an in situ one-step method. Then, MY was used as the core and the antibiotic sulfamethoxazole (SMX) as the template to produce highly selective magnetic yeast-molecularly imprinted polymers (MY@MIPs). The physicochemical properties of MY@MIPs were assessed by Fourier-transform infrared spectroscopy (FT-IR), a vibrating sample magnetometer (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), specific surface area (SBET) determination, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out to compare MY@MIPs with MY and MY@NIPs (magnetic yeast-molecularly imprinted polymers without template), with MY@MIPs showing a better performance in the removal of SMX from water. Adsorption of SMX onto MY@MIPs was described by the pseudo-second-order kinetic model and the Langmuir isotherm, with maximum adsorption capacities of 77 and 24 mg g-1 from ultrapure and wastewater, respectively. Furthermore, MY@MIPs displayed a highly selective adsorption toward SMX in the presence of other pharmaceuticals, namely diclofenac (DCF) and carbamazepine (CBZ). Finally, regeneration experiments showed that SMX adsorption decreased 21 and 34% after the first and second regeneration cycles, respectively. This work demonstrates that MY@MIPs are promising sorbent materials for the selective removal of SMX from wastewater.publishe

Removal of the hormones 17β-estradiol and 17α-ethinylestradiol from aqueous solutions employing a decomposed peat as adsorbent material

REMOVAL OF THE HORMONES 17b-ESTRADIOL AND 17a-ETHINYLESTRADIOL FROM AQUEOUS SOLUTIONS EMPLOYING A DECOMPOSED PEAT AS ADSORBENT MATERIAL. This paper describes the adsorption of 17b-estradiol (E2) and 17a-ethinylestradiol (EE2) from aqueous solution by decomposed peat. The peat presented a good adsorption process, close to 76.2% for E2 removal and approximately 55.0% for EE2. Moreover, the results indicated a probable multi-layered process. Adsorption isotherms were well fitted by Freundlich model. The data were evaluated considering the pseudo-first-order and pseudo-second-order approaches, being the second more significant mechanism in the rate-controlling step. Thermodynamic data revealed that hormones adsorption onto peat is spontaneous under the employed experimental conditions. The results confirmed the potential of this adsorbent to be employed for effluents treatment

Waste-based alternative adsorbents for the remediation of pharmaceutical contaminated waters: Has a step forward already been taken?

When adsorption is considered for water treatment, commercial activated carbon is usually the chosen adsorbent for the removal of pollutants from the aqueous phase, particularly pharmaceuticals. In order to decrease costs and save natural resources, attempts have been made to use wastes as raw materials for the production of alternative carbon adsorbents. This approach intends to increase efficiency, cost-effectiveness, and also to propose an alternative and sustainable way for the valorization/management of residues. This review aims to provide an overview on waste-based adsorbents used on pharmaceuticals' adsorption. Experimental facts related to the adsorption behaviour of each adsorbent/pharmaceutical pair and some key factors were addressed. Also, research gaps that subsist in this research area, as well as future needs, were identified. Simultaneously, this review aims to clarify the current status of the research on pharmaceuticals' adsorption by waste-based adsorbents in order to recognize if the right direction is being taken.publishe