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•Achieved >95% removal of tetracycline in a porous Magnéli phase Ti4O7 anode.•Hydroxyl radical was generated at a rate of 2×10−9molcm−2min−1.•Radical trapping method should be used ...with restrictions to quantify free radicals.•Reaction pathways were proposed using the data of high resolution mass spectrometry.•Toxicity increased at the beginning but reduced during the last stage of treatment.
The goal of this study is to evaluate Magnéli phase titanium oxide (Ti4O7) as an anode material for potential application in electrochemical oxidation of organic pollutants in water. The removal of tetracycline (TC) was systematically investigated in terms of kinetics, reaction mechanisms and pathways, and multi-species toxicity. Application of 0.5–3mAcm−2 current densities resulted in >90% total removal of TC over a wide range of initial concentrations from 1ppm to 50ppm with half-lives between 28mins and 75mins. The oxidation mechanisms were further elucidated using salicylic acid (SA) as a hydroxyl free radical trap. At least 40% of total TC removal was attributable to reactions mediated by hydroxyl radicals, which were generated on Magnéli phase Ti4O7 at a rate of 2×10−9molcm−2min−1 under 0.5mAcm−2 applied current density. Tests on Escherichia coli culture indicated that electro-oxidation of TC by Magnéli phase Ti4O7 anode successfully reduced the original antimicrobial activity to a level below detection limit. However, for freshwater micro algae Scenedesmus obliquus, inhibitory effects persisted in the first couple of hours and then dramatically reduced during the last stage of treatment, likely due to intermediate products that later mineralized and detoxified. Reaction pathways were proposed based on the data of high-resolution mass spectrometry, and oxidation products with antibiotic potency similar to or greater than TC were identified in 1h treatment sample, but not detectable in the end-of-treatment solution.
A novel eco-friendly procedure was developed to produce safer, stable and highly pure zinc oxide nanoparticles (ZnO NPs) using microalgae Chlorella extract. The ZnO NPs were synthesized simply using ...zinc nitrate and microalgae Chlorella extract which conducted at ambient conditions. In this recipe, microalgae Chlorella extract acted as the reducing agent and a stabilizing layer on fresh ZnO NPs. UV-visible spectrum was confirmed the formation of ZnO NPs showing an absorption peak at 362 nm. XRD results demonstrated that prepared ZnO NPs has a high-crystalline hexagonal (Wurtzite) structure, with average size about 19.44 nm in diameter. FT-IR spectral analysis indicated an active contribution of algae-derived biomolecules in zinc ions bioreduction. According to SEM and TEM observations, ZnO NPs are well dispersed and has a hexagonal shape with the average size of 20 ± 2.2 nm, respectively. Based on gas chromatography analyses, the optimum 0.01 g/L dosage of ZnO catalyst revealed an effective photocatalytic activity toward the degradation (97%) of Dibenzothiophene (DBT) contaminant as an organosulfur model in the neutral pH at the mild condition. Rapid separation and facile recyclability at five consecutive runs were demonstrated high efficiency and durability of green ZnO nanophotocatalyst. The possible mechanisms of green ZnO NPs formation and the photo-desulfurization of DBT were also proposed.
The concern regarding alternate sources of energy is mounting day-by-day due to the effect of pollution that is damaging the environment. Algae are a diverse group of aquatic organisms have an ...efficiency and ability in mitigating carbon dioxide emissions and produce oil with a high productivity which has a lot of potential applications in producing biofuel, otherwise known as the third-generation biofuel. These third generation biofuels are the best alternative to the present situation since they have the perspective to eliminate most of the ecological problems created by the use of conventional fossil fuels. These organisms are responsible for closely 50% of the photosynthesis process taking place on the planet and are distributed predominantly in many of the aquatic systems. The huge interest in utilizing these organisms as a potential source of energy lies in converting the primary as well as secondary metabolites into useful products. Algae are considered to be the most prominent resource for the upcoming generations as the most suitable and sustainable feedstock. The key process limitations in microalgal biofuel production are inexpensive and effective harvesting of biomass and extraction of lipids. The major objective of this article is to provide a comprehensive review on various methods of both biomass harvesting and lipid extraction from microalgae available, so far, besides to discuss their advantages and disadvantages. This article also deals with various conditions that are favourable for lipid accumulation as well as the yield from different species.
•Algae are considered as the most prominent resource for the future generations as viable feedstock.•Microalgae act as solar driven energy cell factories and are capable of converting CO2 to O2.•The key limit in microalgae biofuel production is cheap and effective extraction of lipids.•Existing technical viability for the production of biofuels from microalgae has been discussed.•Numerous biomass harvesting and lipid extraction methods were also discussed in detail.
A new route to convert crude microalgae oils using ZrO2-promoted Ni catalysts into diesel-range alkanes in a cascade reaction is presented. Ni nanoparticles catalyze the selective cleavage of the C–O ...of fatty acid esters, leading to the hydrogenolysis of triglycerides. Hydrogenation of the resulting fatty acids to aldehydes (rate-determining step) is uniquely catalyzed via two parallel pathways, one via aldehyde formation on metallic Ni and the second via a synergistic action by Ni and ZrO2 through adsorbing the carboxylic groups at the oxygen vacancies of ZrO2 to form carboxylates and subsequently abstracting the α-hydrogen atom to produce ketene, which is in turn hydrogenated to aldehydes and decarbonylated on Ni nanoparticles.
Towards industrial products from microalgae Ruiz, Jesus; Olivieri, Giuseppe; de Vree, Jeroen ...
Energy & environmental science,
01/2016, Letnik:
9, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Microalgae show an enormous potential as sustainable feedstock for numerous bioproducts. The current work analyzes the feasibility of business cases for different markets of products from microalgae. ...We perform a techno-economic evaluation of the whole process chain including cultivation, biorefinery and market exploitation for a 100 hectares facility in six locations. Our projections show a current cost per unit of dry biomass of 3.4 Euro kg-1 for microalgae cultivation in Spain (excluding biorefining products), with an expected reduction to 0.5 Euro kg-1 in ten years. A sensitivity analysis reveals the roadmap to achieve this. Production of high-value products (e.g. pigments) would be currently profitable, with a net present value of 657 MEuro in 15 years. Markets aimed at food and chemical commodities require further cost reductions for cost competitiveness, reachable in the next decade.
Microalgae-based carbon sequestration has been identified as one of the potential research directions of energy sustainable development in many countries. However, low productivity restricts its ...large-scale development. In order to break through this technical obstacle, it is necessary to study the efficiency of photosynthetic carbon fixation of microalgae from the mechanism level. Firstly, biochemical mechanism of microalgal carbon capture is introduced, representative studies on biological characteristics (especially genetic engineering method for enhancing carbon sequestration of microalgae), response characteristics and efficacy characteristics are reviewed respectively, and the development trends and limitations of this technology are commented; secondly, seven main problems existing in microalgae carbon sequestration are summarized, and the complexity of methodology is demonstrated at the methodological level; finally, solutions to these problems are put forward: further grasp the interdisciplinary characteristics of microalgae carbon fixation efficiency and re-recognize carbon sequestration efficiency of microalgae. And concrete ways to improve carbon sequestration efficiency of microalgae are given.
•Genetic engineering method for enhancing microalgae-based carbon is summarized.•Concrete ways to improve carbon sequestration efficiency of microalgae are given.•The photochemical-in-situ micro-thermal test technical scheme is designed.
•Scenedesmus obliquus was tolerant to SMZ, SMX, and their mixture, and could withstand their high doses.•96 h EC50 of SMZ, SMX, and their mixture for S. obliquus was 1.23, 0.12, and 0.89 mg L-1.•The ...risk quotients of SMZ, SMX, and their mixture were >1.•The removal of SMZ and SMX was more in the mixture than their individual medium.•Metabolic pathways of SMZ and SMX by S. obliquus were proposed.
This study investigated the environmental effects of two common emerging contaminants, sulfamethazine (SMZ) and sulfamethoxazole (SMX), and their mixture using a green microalga, Scenedesmus obliquus. The calculated EC50 values of SMZ, SMX, and their mixture (11:1 wt/wt) after 96 h were 1.23, 0.12, and 0.89 mg L-1, respectively. The toxicity of the mixture could be better predicted using a concentration addition model than an independent action model. The risk quotients of SMZ, SMX, and their mixture were >1 during the experiment, indicating their high potential risks on aquatic microorganisms. Despite their toxicity, S. obliquus exhibited 17.3% and 29.3% removal of 0.1 mg L-1 and 0.2 mg L-1 after 11 days of cultivation. The changes of SMZ and SMX removal were observed when combined, which showed a significantly improved removal of SMZ (up to 3.4 folds) with addition of SMX (0.2 mg L-1). The metabolic pathways of SMZ and SMX were proposed according to mass spectroscopic analysis, which showed six metabolites of SMX and seven intermediates of SMZ, formed as a result of ring cleavage, hydroxylation, methylation, nitrosation, and deamination.
Research studies on microalgae have increased in the last decades due to the wide range of applications associated to these photosynthetic microorganisms. Microalgae are an important source of oils ...and other biomolecules that can be used in the production of biofuels and high-valued products. However, the use of microalgae in these green processes is still not economically viable. One of the main costs associated to microalgal production is related to the harvesting process, as it usually accounts for about 20–30% of total cost. Therefore, this review focuses on the main harvesting processes applied to microalgae, presenting the main advantages and disadvantages of each method, to allow the selection of an appropriate procedure to effectively separate microalgal biomass from the culture medium. To reduce the associated costs, it is common to harvest microalgae in a two-step separation: (i) thickening procedures, in which microalgal slurry is concentrated to about 2–7% of total suspended solids; and (ii) dewatering procedures, which result in the concentration of microalgal slurry to 15–25% of total suspended solids. Selection of the adequate harvesting methods depends on the characteristics of the target microorganism and also on the type and value of the end product.
Algae is a potent renewable source with the favorable characteristics. However, there are still many barriers in the related theory, techniques and industrialization, which lead to the high cost of ...the algae biofuel. This paper reviewed the process of the microalgae biofuel's commercial process. Investigated the barriers of the technologies especially the energy-extensive part and the pilot scale test which is the crucial part of the process. The policy supports of American, EU and China for microalgae biofuel industry and the effect of them was summarized at this paper. Numbers of pilot scale program has launched in the support of the government and the private investment, while there is still some distance from scale up production. Algae fundamental biology research, co-products’ production to make profits in short term, and support from government are key strategies of algae commercialization.
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•Various microalgal-based materials were used for Cr(VI) removal from water.•Higher removal efficiency of Cr(VI) was attained as Cr(VI) was added in lag phase.•Microalgal biochar ...removed 100% of 1, 5 and 10 mg/L initial concentration of Cr(VI).•Desorption efficiency of Cr(VI) from MB-500 with sonication bath was 59.41%.•More than 97% of desorbed Cr(VI) was recovered by barium chloride.
The current study presents a comprehensive comparison towards the potential of different microalgal-based materials for the removal of hexavalent chromium (Cr(VI)) from water. Among the tested materials, microalgal biochar showed the highest removal efficiency (100%) of Cr(VI). The highest monolayer estimated adsorption capacities were 23.98, 25.19 and 24.27 mg/g at 5, 22 and 35 °C, respectively. Experimental data showed good compliance with pseudo-second-order kinetic model. The results of continuous column studies showed that the column removal efficiency increased from 52.33 to 57.58% by increasing the adsorbent dose from 0.125 to 0.200 g. Desorption efficiency of Cr(VI) by 0.1 M NaOH was increased from 51.16 to 59.41% by sonication bath as compared to roller shaker. More than 97% of desorbed Cr(VI) was recovered in less than 10 min by BaCl2. This study shows that non-living microalga materials are more effective than living cells in the removal and recovery of Cr(VI) from water.
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