Biosorption of heavy metal and dyes : a promising technology leather wastewater treatment

The presence of dyes and heavy metals is usual in industrial processes like chrome tanning in tannery industry and their removal may be an environmental problem. Different techniques were developed and applied for the treatment of dyes and heavy metals in effluents. Among them, adsorption showed to be an economic, simple operation and an effective technique. Zeolites have a strong affinity for cations of transition metals, but only little affinity for anions and non-polar organic molecules. The application of a zeolite to heavy metal removal may be improved by the presence of microorganisms. The aim of this work is the treatment of an effluent containing dyes and toxic metals. Several operation parameters such as pH, concentration and kinetic behavior were studied. This innovative process for treating dyes and heavy metal effluents showed that the zeolite-biomass system is able to perform the removal of a combination of Azure B and chromium(VI). A mixture of dye and metal solutions was treated reaching a removal higher than 50% in the case of chromium (VI) and higher than 99% for dye, in 8 days

Application of zeolite-Arthrobacter viscosus system for the removal of heavy metal and dye : chromium and azure B

A hybrid system combining the ion-exchange properties of a NaY zeolite and the characteristics of the bacterium Arthrobacter viscosus was investigated to treat polluted effluents with dye and toxic metals. In this study, the dye and the metal ion employed were a thiazine dye, Azure B, and chromium (VI), respectively. Initially, the removal of dye by the zeolite was tested. The analysis of dye equilibrium isotherms data was done using Langmuir, Freundlich, Sips and Redlich–Peterson models. Redlich–Peterson model gave the better fitting to data. In the dye adsorption studies, pseudo-second order kinetics showed the more reliable results. Operating at the optimised conditions in the treatment of single pollutants, a mixture of dye and metal solutions was treated reaching a removal higher than 50% for chromium (VI) and higher than 99% for dye, in 8 days.This work was supported by Fundacao para a Ciencia e Tecnologia (FCT-Portugal) and Xunta de Galicia under programme 08MDS034 314PR. The authors are grateful to University of Vigo for financial support of the research of Emilio Rosales under a mobility grant

Enhanced selective metal adsorption on optimised agroforestry waste mixtures

The aim of this work is to ascertain the potentials of different agroforestry wastes to be used as biosorbents in the removal of a mixture of heavy metals. Fern (FE), rice husk (RI) and oak leaves (OA) presented the best removal percentages for Cu(II) and Ni(II), Mn(II) and Zn(II) and Cr(VI), respectively. The performance of a mixture of these three biosorbents was evaluated, and an improvement of 10% in the overall removal was obtained (19.25 mg/g). The optimum mixture proportions were determined using simplexcentroid mixture design method (FE:OA:RI = 50:13.7:36.3). The adsorption kinetics and isotherms of the optimised mixture were fit by the pseudo-first order kinetic model and Langmuir isotherm. The adsorption mechanism was studied, and the effects of the carboxylic, hydroxyl and phenolic groups on metal–biomass binding were demonstrated. Finally, the recoveries of the metals using biomass were investigated, and cationic metal recoveries of 100% were achieved when acidic solutions were used.This work has been funded by the Spanish Ministry of Economy and Competitiveness, Xunta de Galicia and ERDF Funds (Projects CTM 2011-25389 and GRC 2013/003). The authors are grateful to Xunta de Galicia for financial support of the researcher Emilio Rosales under a postdoctoral Grant and the Spanish Ministry of Economy and Competitiveness for financial support of the researcher Marta Pazos under a Ramon y Cajal Grant

Removal of Di-(2-ethylhexyl)phthalate (DEHP) from water using a LECA-Pseudomonas putida Biobarrier

The removal and biodegradation of an organic toxic pollutant, di-(2-ethylhexyl) phthalate (DEHP), has been investigated. Initially, a screening of different degrading bacteria has been developed and Pseudomonas putida showed the highest degradation ability. This bacterium was immobilised in an inert support, light expanded clay aggregate (LECA). After the biofilm formation on the LECA, the degradation of DEHP was evaluated operating in a fixed bed reactor. In addition, several studies of DEHP adsorption on LECA were carried out in order to determine the mechanism of the degradation process that takes place. The degradation studies demonstrated that the developed system can be applied to DEHP removal and the degradation is due to adsorption process and the activity of P. putida

¿Es el desarrollo de un proyecto una buena herramienta para aprender los principios fundamentales de una materia?

Hoy en día, se requiere el uso de herramientas efectivas que refuercen el aprendizaje de los estudiantes. Un ejemplo claro es el uso de Aprendizaje basado en el desarrollo de un proyecto a escala real (ABDPER). ABDPER implica un estudio en profundidad de una situación particular y la utilización de los conceptos adquiridos durante el año académico. La principal ventaja de la enseñanza con ABDPER es que los estudiantes participan activamente en la comprensión de los principios al abstraerse de la teoría enseñada a través del razonamiento inductivo. En nuestro caso, ABDPER se ha aplicado a diversas materias, si bien en este trabajo se expondrá los resultados obtenidos en la materia Reactores y Biotecnología. Para esta propuesta, los estudiantes aplican el conocimiento gradual adquirido durante el semestre al diseño y escalado de una planta de producción industrial e implementarán en el desarrollo del mismo los avances de I+D y las Mejores Tecnologías Disponibles (MTD). La respuesta de los estudiantes ha sido muy positiva a esta nueva metodología y se puede concluir que el uso de esta tecnología basada en artículos de investigación científica aumentó las habilidades de los estudiantes en el marco de la asignatura

Application of deep eutectic solvents (DES) for the synthesis of iron heterogeneous catalyst: application to sulfamethoxazole degradation by advanced oxidation processes

The development of novel approaches to the remotion of pharmaceuticals in wastewater is a subject of concern due to their effect on living beings and the environment. Advanced oxidation processes and the use of relevant catalysts are feasible treatment alternatives that require further development. The development of suitable heterogeneous catalysts is a necessity. This work proposes the synthesis of an iron catalyst in a deep eutectic solvent (Fe-DES) composed of choline chloride and citric acid, which was physically and chemically characterized using SEM-EDS and TEM, FTIR, RAMAN, XRD and XPS. The characterisation confirmed the presence of iron in the form of hematite. Fe-DES was shown to be a multipurpose catalyst that can be applied in the removal of sulfamethoxazole as a reagent in the Fenton and electro-Fenton processes and as an activator of peroxymonosulfate (PMS) processes. After testing the catalyst with the aforementioned techniques, the best result was achieved by combining these processes in an electro-PMS, with great efficiency achieved by dual activation of the PMS with the catalyst and electric field, attaining total elimination at natural pH in 90 min. Furthermore, the degradation was confirmed by the detection of short-chain carboxylic acids (oxalic, succinic, and acetic) and reduction in toxicity values. These results confirm the suitability of Fe-DES to degrade high-priority pharmaceutical compounds.Xunta de Galicia y FEDER | Ref. ED431C 2021-43Ministerio de Ciencia e Innovación | Ref. PCI2022-132941Ministerio de Ciencia e Innovación | Ref. PDC2021-121394-I0

Immobilization of esterase from Bacillus subtilis on Halloysite nanotubes and applications on dibutyl phthalate degradation

Dibutyl phthalate (DBP) is one of the listed phthalic acid esters (PAEs) known as the priority toxicants which exhibit carcinogenic and teratogenic properties and is responsible for endocrine disruption. Therefore, its removal has become a matter to tackle with. In this work, the feasibility of DBP degradation by esterase and lipase enzymes obtained from various microorganisms and the immobilization of the most effective in a clayey material were investigated. Esterase from Bacillus subtilis exhibited the highest degradation efficiency reaching a complete degradation. Its immobilization onto halloysite nanotubes (HNTs) by adsorption method was studied by response surface methodology using a central composite design face-centered. The four selected factors that affect the HNT-enzyme composite generation were: pH, adsorption time, enzyme/HNT (E/H) ratio, and adsorption temperature, and the optimal conditions were determined (pH 7, time 360 min, E/H ratio 0.2, temperature 30ºC). Consequently, the activity did not significantly decrease by immobilization, and the adsorption efficiency and relative activity were determined to be 73.15% and 82.7%, respectively. Besides, the immobilization enhanced thermal and storage stability. As for enzyme reusability, after 7 continuous cycles, the composite maintained almost 75% of its initial activity. Both the free enzyme (1 mg/mL) and the composite degraded 100 mg/L DBP with 100% efficiency and several byproducts were detected. Moreover, the composite could be reused for 7 cycles keeping a remarkable catalytic activity. Overall, this study indicated that the HNT-enzyme composite may be used as an effective candidate for remediation of the environmental media contaminated with DBP and other PAEs.Agencia Estatal de Investigación | Ref. PCI2022-132941Xunta de Galicia | Ref. ED431C 2021-43Universidade de Vigo/CISU

Continuous treatment of diethyl hexyl and dibutyl phthalates by fixed-bed reactor: comparison of two esterase bionanocomposites

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe removal of Diethyl hexyl phthalate (DEHP) and Dibutyl phthalate (DBP) is of great importance due to their potential adverse effects on the environment and human health. In this study, two bionanocomposites prepared by immobilization of Bacillus subtilis esterase by crosslinking to halloysite and supported in chitosan and alginate beads were studied and proposed as a green approach. The esterase immobilization was confirmed by physical–chemical characterization. Bionanocomposite using chitosan showed the best degradation levels in batch tests attaining complete degradation of DBP and around 90% of DEHP. To determine the operational stability and efficiency of the system, two fixed bed reactors filled with both bionanocomposites were carried out operating in continuous mode. Chitosan based bionanocomposite showed the best performance being able to completely remove DBP and more than 85% of DEHP at the different flowrates. These results proved the potential of these synthesized bionanocomposites to effectively remove Phthalic Acid Esters.Xunta de Galicia | Ref. ED431C 2021-43Agencia Estatal de Investigación | Ref. PCI2022-13294

Continuous adsorption studies of pharmaceuticals in multicomponent mixtures by agroforestry biochar

In this study, the adsorption of a multicomponent mixture of active pharmaceutical compounds, such as Venlafaxine (VLX), Trazodone (TRZ) and Fluoxetine (FLX), was studied in a biochar fixed-bed column. The selection of appropriate biochar (eucalyptus, grapevine cane and holm tree biochar) as an adsorbent was carried out through batch assays. An insight into the adsorption mechanism and its correlation with the chosen biochars was performed, showing that electron donor/acceptor interaction is the main mechanism involved. Equilibrium and kinetic batch adsorption experiments were performed and the results demonstrated that eucalyptus biochar was the most viable option for the removal of the pollutants, individually and combined. Column adsorption experiments were performed and Thomas, Yoon-Nelson and Yan models were adjusted to the breakthrough curves. This multicomponent system exhibited a synergetic behavior for TRZ and an antagonist for VLX and FLX, when compared to the single and multicomponent systems previously evaluated in batch assays. The treatment of real wastewaters, spiked with pollutants, has demonstrated the removal efficiency of multicomponent mixtures. Finally, the adsorbent regeneration by elution in different solutions was also investigated and methanol proved to be the most effective eluent for the column regenerationThis work has been finantially supported by the project CTM2017-87326-R funded by MCIN/ AEI/10.13039/501100011033/ FEDER "Una manera de hacer Europa", project ED431C 2021/43 funded by Xunta de Galicia and ERDF, and ERA-NET Cofund WaterWorks2015 Call funded by the EU and FCT/UEFISCDE/FORMAS through the REWATER International Research project. This work was also supported by UIDB/50006/2020 and UIDP/50006/2020 by the Fundação para a Ciência e a Tecnologia (FCT Portugal)/Ministério da Ciência, Tecnologia e Ensino Superior (MCTES Portugal) through national funds. Manuela M. Moreira (project CEECIND/02702/2017) also acknowledge for her financial support financed by national funds through FCT and to REQUIMTE/LAQV. Funding for open access charge: Universidade de Vigo/CISUGinfo:eu-repo/semantics/publishedVersio

Heterogeneous Electro-Fenton-like designs for the disposal of 2-phenylphenol from water

The hunt for efficient and environmentally friendly degradation processes has positioned the heterogeneous advanced oxidation processes as an alternative more interesting and economical rather than homogenous processes. Hence, the current study lies in investigating the efficiency of different heterogeneous catalysts using transition metals in order to prevent the generation of iron sludge and to extend the catalogue of possible catalysts to be used in advanced oxidation processes. In this study, nickel and zinc were tested and the ability for radical-generation degradation capacity of both ions as homogeneous was evaluated in the electro-Fenton-like degradation of 2-phenylphenol. In both cases, the degradation profiles followed a first-order kinetic model with the highest degradation rate for nickel (1 mM) with 2-phenylphenol removal level of 90.12% and a total organic reduction near 70% in 2 h. To synthesise the heterogeneous nickel catalyst, this transition metal was fixed on perlite by hydrothermal treatment and in a biochar or carbon nanofibers by adsorption. From the removal results using the three synthesized catalysts, it is concluded that the best catalysts were obtained by inclusion of nickel on biochar or nanofibers achieving in both with removal around 80% before 1 h. Thus, to synthetize a nickel electrocatalyst, nickel doped nanofibers were included on carbon felt. To do this, the amount of carbon black, nickel nanofibers and polytetrafluoroethylene to add on the carbon felt was optimized by Taguchi design. The obtained results revealed that under the optimised conditions, a near-complete removal was achieved after 2 h with high stability of the nickel electrocatalyst that open the applicability of this heterogeneous system to operate in flow systems.Ministerio de Ciencia e Innovación | Ref. PDC2021-121394-I00Ministerio de Ciencia e Innovación | Ref. CTM 2017-87326-RXunta de Galicia | Ref. ED431C 2021-4