Facile one-step synthesis of a versatile nitrogen-doped hydrochar from olive oil production waste, “alperujo”, for removing pharmaceuticals from wastewater

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGIn line with the principles of zero waste and recycling, alperujo (AL) was used in this study to produce a value-added product: hydrochar (HC) with high adsorption capacity. An optimization of the hydrothermal carbonization (HTC) conditions, such as temperature, residence time, and water/solid ratio, was carried out to maximize the adsorption capacity. Eight HCs were obtained, and an in-depth comparative characterization, as well as adsorption tests of two pharmaceuticals with very different physicochemical properties (fluoxetine (FLX) and cefazolin (CFZ)), were performed. This first step allowed for elucidation of the best candidates to carry out nitrogen grafting on their surface, resulting in the HC obtained at a higher water/solid ratio and temperature, and longer residence time: 3-220°C-2.5 h with a maximum uptake of 4.6 and 0.4 mg/g for FLX and CFZ, respectively. After that, a facile one-step, one-pot synthesis of nitrogen-doped hydrochars (N-HC) was developed to prepare a versatile bio-adsorbent with enhanced adsorption capacity. Two N–HCs were prepared using urea (U-HC) and polyethyleneimine (PEI-HC) and were intensively characterized to shed light on the adsorption mechanism. In both cases, amide groups were formed, which favored the adsorption process. PEI-HC acquired an outstanding maximum adsorption capacity of 983.84 mg/g for CFZ, and 29.31 mg/g for FLX, and the process was well described by the Freundlich isotherm and pseudo-second-order kinetic model. A co-adsorption test was performed using PEI-HC for both pharmaceuticals, finding that the adsorption process occurs in different active sites because there was no interference between the pollutants. This fact corroborates the versatility of the new bio-adsorbent synthesized.Ministerio de Ciencia e Innovación | Ref. PID 2020- 113667GBI00Ministerio de Ciencia e Innovación | Ref. PDC 2021-121394-I00Xunta de Galicia | Ref. ED431C 2021-43Universidade de Vigo/CISU

On-site regeneration by ultrasound activated persulfate of iron-rich Antipyrine-loaded biochar

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGAdsorption process has proven its efficiency in the abatement of pharmaceuticals in liquid media, even if large volumes of wastewater need to be treated. Nevertheless, exhausted adsorbent regeneration is economically and environmentally necessary. For this reason, recent studies are aimed at finding new methods of regeneration. In this study, an on-site adsorption-regeneration method was assessed. Initially, a model pharmaceutical, Antipyrine (Apy), has been adsorbed onto a low-cost biochar. Apy adsorption followed a pseudo-second order kinetic and a Langmuir isotherm. In a second step, spent biochar was regenerated by oxidation using SO4- . To do this, SO4- was generated by activation of persulfate by ultrasound and assisted by the iron inherently into the biochar. To facilitate the availability of this iron, the addition of an enhancing agent such as oxalic acid was evaluated. The regenerated biochar proved its stability and reusability achieving an uptake percentage of around 87% after the third adsorption-regeneration cycle. Therefore, this on-site regeneration method could be promising for treating other kinds of adsorbents and resolving the pollution problems caused by the non-controlled throw of the exhausted adsorbents.Agencia Estatal de Investigación | Ref. PID2020-113667GB-I00Agencia Estatal de Investigación | Ref. PDC2021-121394-I00Xunta de Galicia | Ref. ED431C 2021-4

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

From waste to resource: valorization of lignocellulosic agri-food residues through engineered hydrochar and biochar for environmental and clean energy applications—a comprehensive review

Agri-food residues or by-products have increased their contribution to the global tally of unsustainably generated waste. These residues, characterized by their inherent physicochemical properties and rich in lignocellulosic composition, are progressively being recognized as valuable products that align with the principles of zero waste and circular economy advocated for by different government entities. Consequently, they are utilized as raw materials in other industrial sectors, such as the notable case of environmental remediation. This review highlights the substantial potential of thermochemical valorized agri-food residues, transformed into biochar and hydrochar, as versatile adsorbents in wastewater treatment and as promising alternatives in various environmental and energy-related applications. These materials, with their enhanced properties achieved through tailored engineering techniques, offer competent solutions with cost-effective and satisfactory results in applications in various environmental contexts such as removing pollutants from wastewater or green energy generation. This sustainable approach not only addresses environmental concerns but also paves the way for a more eco-friendly and resource-efficient future, making it an exciting prospect for diverse applications.Agencia Estatal de Investigación | Ref. PDC2021-121394-I00Agencia Estatal de Investigación | Ref. PCI2022-132941Agencia Estatal de Investigación | Ref. PID2020-113667GB-I00Xunta de Galicia | Ref. ED431C 2021-43Universidade de Vig

Disinfection through advance oxidation processes: optimization and application on real wastewater matrices

Disinfection is an essential and significant process for water treatment to protect the environment and human beings from pathogenic infections. In this study, disinfection through the generation of hydroxyl (Fenton process (FP)) and sulfate (Fenton-like process (FLP)) radicals was validated and optimized. The optimization was carried out in synthetic water through an experimental design methodology using the bacteria Escherichia coli as a model microorganism. Different variables were evaluated in both processes: precursor concentration (peroxymonosulfate (PMS) and H2O2), catalyst concentration (Fe+2), and pH in the Fenton process. After that, the optimized conditions (FP: 132.36 mM H2O2, 0.56 mM Fe+2 and 3.26 pH; FLP: 3.82 mM PMS and 0.40 mM Fe+2) were applied to real matrices from wastewater treatment plants. The obtained results suggest that both processes are promising for disinfection due to the high oxidant power of hydroxyl and sulfate radicals.Ministerio de Ciencia e Innovación | Ref. PDC2021-121394-I00Ministerio de Ciencia e Innovación | Ref. PID2020-113667GB-I0

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

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

GO-TiO2 as a highly performant photocatalyst maximized by proper parameters selection

The synthesis and characterization of novel graphene oxide coupled to TiO2 (GO-TiO2) was carried out in order to better understand the performance of this photocatalyst, when compared to well-known TiO2 (P25) from Degussa. Thus, its physical-chemical characterization (FTIR, XRD, N2 isotherms and electrochemical measurements) describes high porosity, suitable charge and high electron mobility, which enhance pollutant degradation. In addition, the importance of the reactor set up was highlighted, testing the effect of both the irradiated area and distance between lamp and bulb solution. Under optimal conditions, the model drug methylthioninium chloride (MC) was degraded and several parameters were assessed, such as the water matrix and the catalyst reutilization, a possibility given the addition of H2O2. The results in terms of energy consumption compete with those attained for the treatment of this model pollutant, opening a path for further research.Xunta de Galicia | Ref. ED481B 2019/091Ministerio de Ciencia e Innovación | Ref. PID2020-113667GB-I0

Peroxymonosulfate activation by different synthesized CuFe-MOFs: application for dye, drugs, and pathogen removal

In this study, three CuFe-MOFs were successfully synthesized by a solvothermal process by changing the ratio of solvents, salts, or temperature. These MOFs named CuFe(BDC-NH2)R, CuFe(BDC-NH2)S, and CuFe(BDC-NH2)D showed rod-shaped, spindle-like, and diamond-like structures, respectively. The CuFe(BDC-NH2)D and CuFe(BDC-NH2)S were found to exhibit an improved PMS activation for Rhodamine B removal attaining levels around 92%. Their effective removal capability was investigated as a function of the pH, catalyst dosage, and the effect of the application of UV radiation. The best degradation system was photo-assisted activation of PMS when CuFe(BDC-NH2)D and CuFe(BDC-NH2)S were used. Under these conditions, the degradation of a mixture of antibiotic and anti-inflammatory drugs (sulfamethoxazole and antipyrine) was evaluated with the results revealing the total degradation of both drugs after 1 h. A higher antibacterial activity was attained with the system CuFe(BDC-NH2)R/PMS due to the high copper content with respect to the others.Ministerio de Ciencia e Innovación | Ref. PCI2022-132941Ministerio de Ciencia e Innovación | Ref. PID2020-113667GBI00Xunta de Galicia | Ref. ED431C 2021-4

Electric field as a useful tool to improve the poor adsorption affinity of pollutants on carbonaceous aerogel pellets

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe removal of ionisable drugs (fluoxetine, sulfamethizole and antipyrine) from aqueous solution was performed by conventional adsorption using carbonaceous aerogel pellets as adsorbents. Although >96 % elimination was achieved for sulfamethizole and antipyrine after 1440 min, only 2.5 % fluoxetine was removed. In a multicomponent system, the presence of these three drugs in the solution leads to a fivefold depletion of the adsorbed total mass. Thus, the authors proposed to influence the traditional adsorption process by an electric field to improve the low affinity of fluoxetine to the aerogel. Specifically, the electrosorptive removal of fluoxetine was investigated by applying different voltages between 0.8 and 1.3 V, with the maximum adsorption achieved at 1.2 V. The application of an electric field increases the affinity of the contaminants to aerogel pellets. After demonstrating the applicability of the electrosorption in the removal of fluoxetine, the effect of the water matrix on the process was analysed. For this purpose, the removal of these ionisable drugs was evaluated using real wastewater, specifically, raw wastewater and wastewater after primary and tertiary treatment from a municipal wastewater treatment plant. As expected, pollutant removal was somewhat lower due to the complexity of the water matrix. Total percent removal of all pollutants was achieved using only the effluent treated water as the matrix due to minimal competitive adsorption. Finally, the Microtox® test confirmed the excellent ability of this approach to remove these pharmaceuticals, resulting in luminescence inhibition that decreased by 60–80 % depending on the water matrix compared to the polluted influent.Agencia Estatal de Investigación | Ref. PDC2021-121394-I00Agencia Estatal de Investigación | Ref. PID2020-113667 GB-I00Xunta de Galicia | Ref. ED431C 2021-43Xunta de Galicia | Ref. ED481B 2018/09