Browsing by Author "Freitas, Olga"
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- Acid-base treated vermiculite as high performance adsorbent: Insights into the mechanism of cationic dyes adsorption, regeneration, recyclability and stability studiesPublication . Stawiński, Wojciech; Węgrzyn, Agnieszka; Dańko, Tomasz; Freitas, Olga; Figueiredo, Sónia; Chmielarz, LucjanAdditional treatment with NaOH of acid activated vermiculite results in even higher increase in the adsorption capacity in comparison to samples modified only in acidic solution (first step of activation) with respect to raw material. Optimization of treatment conditions and adsorption capacity for two cationic dyes (methylene blue (MB) and astrazon red (AR)), also as binary mixture, was evaluated. The capacity, based on column studies, increased from 48 ± 2 to 203 ± 4 mg g-1 in the case of methylene blue and from 51 ± 1 to 127 ± 2 mg g-1 in the case of astrazon red on starting and acid-base treated material, respectively. It was shown that adsorption mechanism changes for both cationic dyes after NaOH treatment and it results in decrease of adsorption rate. In binary mixtures methylene blue is bound stronger by adsorbent and astrazon red may be removed in initial stage of adsorption. Extensive studies on desorption/regeneration process proved high efficiency in recyclable use of all materials. Although cation exchange capacity decreases due to acid treatment, after base treatment exchange properties are used more efficiently. On the other hand, increased specific surface area has less significant contribution into the adsorption potential of studied materials. Obtained adsorbents worked efficiently in 7 adsorption-regeneration cycles and loss of adsorption capacity was observed only in two first cycles.
- Adsorption of Fluoxetine and Venlafaxine onto the Marine Seaweed Bifurcaria bifurcataPublication . Silva, Andreia; Stawiński, Wojciech; Romacho, Juan; Santos, Lúcia H.M.L.M.; Figueiredo, Sónia; Freitas, Olga; Delerue-Matos, CristinaMarine macroalga Bifurcaria bifurcata was investigated as sorbent for two environmental emerging pollutants, the pharmaceuticals venlafaxine (VLF) and fluoxetine (FLX), from aqueous solutions, both in mono and bicomponent batch systems. The alga was characterized by means of IR spectroscopy, allowing to identify the most important groups for biosorption, carboxylic, sulfonic and hidroxile. The point of zero charge was determined, being 6.4. Adsorption of FLX follows a pseudo first order kinetics and kinetic constants are higher for FLX than for VLF. Its adsorption better represented by the pseudo second order model. For both pharmaceuticals, the equilibrium was reached within *100 min. Adsorption studies reveal that the process was more efficient at lower pH range and followed the Langmuir–Freundlich’s model for VLF and Langmuir’s model for FLX. Maximum adsorption capacities reached a level of 12 – 3 and 22 – 4 lmol/g for VLF and FLX, respectively, in the mono-component system. The difference was attributed to the presence of various functional groups of varying polarity within the adsorbates’ molecules that affected their interactions with the adsorbent surface. The Langmuir–Freundlich’s extended model was applied to the adsorption data of the bicomponent system and no changes in the maximum adsorption capacities were found (14 – 2 and 20 – 3 lmol/g for VLF and FLX, respectively), there is no evidence of competition between the adsorbates.
- Application of vermiculite-derived sustainable adsorbents for removal of venlafaxinePublication . Silva, Andreia; Martinho, Sílvia; Stawiński, Wojciech; Węgrzyn, Agnieszka; Figueiredo, Sónia; Santos, Lúcia H. M. L. M.; Freitas, OlgaRemoval of emerging pollutants, such as pharmaceuticals, from wastewater is a challenge. Adsorption is a simple and efficient process that can be applied. Clays, which are natural and low-cost materials, have been investigated as adsorbent. In this work, raw vermiculite and its three modified forms (expanded, base, and acid/base treated) were tested for removal of a widely used antidepressant, venlafaxine. Adsorption kinetics followed Elovich's model for raw vermiculite while the pseudo-2nd order model was a better fit in the case of other materials. Equilibrium followed Langmuir's model for the raw and the acid/base-treated vermiculite, while Redlich-Peterson's model fitted better the expanded and the base-treated materials. The adsorption capacity of vermiculite was significantly influenced by the changes in the physical and chemical properties of the materials caused by the treatments. The base-treated, raw, and expanded vermiculites showed lower maximum adsorption capacities (i.e., 6.3 ± 0.5, 5.8 ± 0.7, 3.9 ± 0.2 mg g-1, respectively) than the acid/base-treated material (33 ± 4 mg g-1). The acid/base-treated vermiculite exhibited good properties as a potential adsorbent for tertiary treatment of wastewater in treatment plants, in particular for cationic species as venlafaxine due to facilitation of diffusion of the species to the interlayer gallery upon such treatment. Graphical abstract ᅟ.
- Dual-function hydrotalcite-derived adsorbents with sulfur storage properties: Dyes and hydrotalcite fate in adsorption-regeneration cyclesPublication . Stawiński, Wojciech; Węgrzyn, Agnieszka; Freitas, Olga; Chmielarz, Lucjan; Figueiredo, SóniaThermal treatment of hydrotalcite at increasing temperatures resulted in formation of mixed oxides that exhibited different adsorption behavior toward anionic and cationic industrial dyes. The material annealed at 450 °C was characterized by the highest maximum adsorption capacity for both types of dyes. The adsorption was strongly pH dependent and for the anionic dye abatement low pH was favored whilst higher pH was more preferable for removal of the cationic dye. According to the equilibrium experiments, the maximum adsorption capacity increased from 179 ± 5 to 291 ± 8 mg g−1 in case of the anionic dye at pH 3.5 and from 6 ± 2 to 48 ± 2 mg g−1 in case of the cationic dye at pH 8.0, on starting and thermally treated material at 450 °C, respectively. Detailed characteristics of spent adsorbent and its reconstructed form revealed that after each cycle of adsorption and thermal regeneration the maximum adsorption capacity of the material decreased due to changes in the structure and accumulation of sulfur compounds. Evolution of specific surface area and porosity was correlated with annealing temperatures and behavior of dye's residues.
- Fluoxetine and Nutrients Removal from Aqueous Solutions by PhycoremediationPublication . Silva, Andreia; Fernandes, Diana F.; Figueiredo, Sónia; Freitas, Olga; Delerue-Matos, CristinaThe tertiary treatment using microalgae offers an attractive alternative to the removal of low but relevant concentrations of pharmaceuticals from domestic wastewaters. The removal of fluoxetine from aqueous solutions by living and non-living (lyophilized) Chlorella vulgaris was assessed. The determination of the pH at the point of zero charge, Fourier transmittance infrared analysis, and scanning electron microscopy were performed to characterize the microalgae biomass. Kinetic and equilibrium experiments were performed. The pseudo-second-order model described the kinetics of fluoxetine. The corresponding kinetic constants indicated that biosorption was faster onto non-living biomass than onto living biomass. The equilibrium results showed that the systems followed the Langmuir isotherm model. The maximum capacity of living microalgae (1.9 ± 0.1 mg·g−1) was slightly higher than the non-living microalgae (1.6 ± 0.2 mg·g−1). Living Chlorella vulgaris, free and immobilized in calcium-alginate, were also used to remove fluoxetine and nutrients (nitrogen and phosphorus) from treated municipal wastewater in a batch system. In both experiments, fluoxetine was completely removed within six days. The total phosphorus (TP) and total nitrogen (TN) removal efficiencies achieved for free and immobilized cells were, null and 65.0 ± 0.1%, and 86.2 ± 0.1% and 81.8 ± 3.1, respectively
- Fluoxetine Removal from Aqueous Solutions Using a Lignocellulosic Substrate Colonized by the White-Rot Fungus Pleurotus ostreatusPublication . Silva, Andreia; Sousa, Juliana; Hultberg, Malin; Figueiredo, Sónia; Freitas, Olga; Delerue-Matos, CristinaOne of the main challenges in both the design of new wastewater treatment plants and the expansion and improvement of existing ones is the removal of emerging pollutants. Therefore, the search for economic and sustainable treatments is needed to enhance the removal of pharmaceuticals. The potential of a lignocellulosic substrate colonized by Pleurotus ostreatus, a waste from mushroom production, to remove fluoxetine from aqueous solutions was studied. Batch assays were performed to remove 600 µg∙L−1 fluoxetine from aqueous solutions using the colonized mushroom substrate (CMS) and crude enzyme extracts. The removal efficiencies achieved were, respectively, ≥83.1% and 19.6% in 10 min. Batch assays with sterilized CMS and 1-aminobenzotriazole (to inhibit cytochrome P450 enzymes) showed that the higher removal efficiencies achieved in the CMS assays may be attributed to the synergistic contribution of biosorption onto the CMS and lignin modifying enzymes activity, namely laccase activity. A column assay was performed with the CMS, fed with 750 µg∙L−1 fluoxetine aqueous solution. The removal efficiency was 100% during 30 min, decreasing to a final value of 70% after 8 h of operation. The results suggested that CMS can be a promising eco-friendly alternative to remove fluoxetine from aqueous solutions
- Green Microalgae Scenedesmus Obliquus Utilization for the Adsorptive Removal of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) from Water SamplesPublication . Silva, Andreia; Coimbra, Ricardo N.; Escapa, Carla; Figueiredo, Sónia; Freitas, Olga; Otero, MartaIn view of the valorisation of the green microalga Scenedesmus obliquus biomass, it was used for the biosorption of two nonsteroidal anti-inflammatory drugs, namely salicylic acid and ibuprofen, from water. Microalgae biomass was characterized, namely by the determination of the point of zero charge (pHPZC), by Fourier transform infrared (FT-IR) analysis, simultaneous thermal analysis (STA) and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Kinetic and equilibrium batch experiments were carried out and results were found to fit the pseudo-second order equation and the Langmuir isotherm model, respectively. The Langmuir maximum capacity determined for salicylic acid (63 mg g−1) was larger than for ibuprofen (12 mg g−1), which was also verified for a commercial activated carbon used as reference (with capacities of 250 and 147 mg g−1, respectively). For both pharmaceuticals, the determination of thermodynamic parameters allowed us to infer that adsorption onto microalgae biomass was spontaneous, favourable and exothermic. Furthermore, based on the biomass characterization after adsorption and energy associated with the process, it was deduced that the removal of salicylic acid and ibuprofen by Scenedesmus obliquus biomass occurred by physical interaction.
- Removal of diclofenac and sulfamethoxazole from aqueous solutions and wastewaters using a three-dimensional electrochemical processPublication . Soares, Cristina; Correia-Sá, Luísa; Paíga, Paula; Barbosa, Carlos; Remor, Paula Verônica; Freitas, Olga; Moreira, Manuela M.; Nouws, Henri; Correia, Manuela; Ghanbari, Amir; Rodrigues, António J.; Oliveira, Carlos M.; Figueiredo, Sónia; Delerue-Matos, CristinaThe three-dimensional (3D) electrochemical treatment process was studied for the removal of two pharmaceuticals, diclofenac (anti-inflammatory) and sulfamethoxazole (antibiotic), in mono and bi-component systems. Adsorption and conventional two-dimensional electrochemical processes were initially studied and then combined to develop the 3D process. The influence of different operating parameters on the removal efficiency was studied: the distance between the cathode and the anode, the pharmaceutical and electrolyte (NaCl) concentrations, the pH, and the (carbon-based) adsorbent used as particulate electrode (biochar and commercial activated carbon, granulometry, and amount). The energy consumption and the electric energy per order were evaluated. The results demonstrate the efficiency of the 3D process for the removal of diclofenac and sulfamethoxazole from aqueous solutions, both for mono- and bi-component systems, achieving their complete removal respectively in 10 and 30 min, using a Mixed Metal Oxide anode (titanium-coated with RuO2-IrO2-TiO2), a stainless steel cathode, a biochar particulate electrode (1–2 mm), an initial pharmaceutical concentration of 10 mg/L, an inter-electrode distance of 7.5 cm, a pH value of 7 and a current density of 7 mA/cm2. The optimised 3D process was also successfully applied to a wastewater treatment plant effluent, but lower removal efficiencies were observed (after 30 min) for bi-component fortified samples; 49% for DCF and 86% for SMX, with energy consumptions of 1224 and 613 Wh/g and an electric energy per order of 19.1 and 8.77 kWh/m3 respectively. On the other hand, the pharmaceuticals were completely removed from the effluent when real concentrations (i.e. without their addition) were used
- Simultaneous removal of dyes and metal cations using an acid, acid-base and base modified vermiculite as a sustainable and recyclable adsorbentPublication . Stawiński, Wojciech; Węgrzyn, Agnieszka; Freitas, Olga; Chmielarz, Lucjan; Mordarski, Grzegorz; Figueiredo, SóniaThe aimof thiswork was the modification of vermiculite in order to produce a lowcost, efficient and sustainable adsorbent for dyes and metals. Three activation methods consisting of acid, base and combined acid/base treatment were applied to improve the of vermiculite's adsorption properties. Adsorbents were tested in single, biand tricomponent solutions containing cationic dyes and Cu2+ cations. The rawmaterial showed lowadsorption capacity for dyes and metal. The acid/base treated vermiculite had very good adsorption capacity toward dyes while the maximumadsorption capacity for Cu2+ did not change comparing to the startingmaterial. The alkaline treated vermiculite was a good adsorbent for metals,while still being able to remove dyes on the level of the not treated material. Moreover, it was shown that the materials may be regenerated and used in several adsorptiondesorption cycles. Furthermore, itwas possible to separate adsorbed dyes from metals thatwere desorbed, using as eluents ethanol/NaCl and 0.05MHNO3, respectively. This opens a possibility for sustainable disposal and neutralization of both of the pollutants or for their further applications in other processes.
- Study of adsorptive materials obtained by wet fine milling and acid activation of vermiculitePublication . Węgrzyn, Agnieszka; Stawiński, Wojciech; Freitas, Olga; Komędera, Kamila; Błachowski, Artur; Jęczmionek, Łukasz; Dańko, Tomasz; Mordarski, Grzegorz; Figueiredo, SóniaWet fine milling, as a pretreatment step to acid activation of vermiculite, was applied in order to decrease the environmental impact of the procedure commonly used to increase the mineral's adsorption capacity. Milling caused fragmentation of the material and several changes in its structure: edges of the flocks became frayed, the surface cracked, cation exchange capacity (CEC) increased, and most of the iron in oligonuclear and bulk form was removed. At the same time the specific surface area, crystallinity, chemical composition and adsorption capacity did not change significantly. Fine ground material was more susceptible to acid activation, which caused a decrease in the crystallinity and CEC, development of meso- and microporosity, an increase in the total volume of pores, in the specific surface and external surface areas. Micropores were developed faster in lower acid concentrations in the rough ground material, while the external surface area and total pores volume increased faster in the fine ground vermiculite. The latter material also had a higher CEC. Application of 0.5 mol L− 1 HNO3 to rough ground vermiculite did not change its adsorption capacity, however it changed from 55 ± 7 to 110 ± 8 mg g− 1 when the material was fine ground. The optimal treatment conditions for both materials were obtained for 1.0 mol L− 1 HNO3, however the adsorption capacity for the fine ground vermiculite increased more (i.e., from 55 ± 7 to 136 ± 7 mg g− 1) than for its rough ground counterpart (i.e., 52 ± 7 to 93 ± 7 mg g− 1). Concentrations higher than 1.0 mol L− 1 resulted in deterioration of the adsorption capacities in both cases. Considering all the experimental outcomes, it can be concluded that the environmental impact of acid activation of vermiculite may be diminished by application of fine grinding of the material before the chemical activation process. Such treatment resulted in higher adsorption capacity at a given acid concentration compared to the rough ground material.