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Bacterially produced polyhydroxyalkanoates are valuable substitutes for petrochemical plastics, but their current production capacities are very scarce. Producing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-co-HV) from methane and odd-chain carbon fatty acids could make the production of this biodegradable polymer cost-effective. This study analyzes the main factors affecting methanotrophic growth and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) accumulation, simulating a pilot-scale process based on a double-stage approach. The effects of the nitrogen source and the oxygen partial pressure during a 20 day growth phase were studied; the cosubstrate concentration, the culture selected, and the methane partial pressure were investigated during the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production stage performed within 15 days under nutrient starvation. Methylocystis parvus OBBP and Methylosinus thricosporum OB3b reached the maximum growth productivities with ammonium as the nitrogen source and oxygen at high partial pressure. The simulation of the PHB-co-HV accumulation revealed that methanotrophs could better accumulate the polymer with low valeric acid concentrations. A methane-abundant gas stream (0.5 atm of methane) could increase process yields up to 0.32 kg m-3 d-1. © 2022 The Authors. Published by American Chemical Society.

Bacterially produced polyhydroxyalkanoates are valuable substitutes for petrochemical plastics, but their current production capacities are very scarce. Producing poly(3-hydroxybutyrate

In this paper, the retarding effect of a green additive, citric acid, towards calcium carbonate scale deposition is studied. Scale formation is one of the most common causes of malfunctions in process equipment. This is the reason it is crucial to retard scale precipitation, that is, in order to reduce economic damages. With this additive in the solution, experimental runs have been carried out in supersaturation conditions in terms of concentration of calcium carbonate at equilibrium, with a supersaturation ratio ranging from 16 to 280, at 25°C. Three different concentrations of citric acid have been investigated (0.520 × 10−3, 1.041 × 10−3 and 1.561 × 10−3 M) in a laboratory scale plant. Comparing results obtained in terms of induction time with previous experimental runs, performed without additives, citric acid has shown its significant capacity to retard calcium carbonate precipitation, by increasing induction time values. This behaviour is enhanced by raising the additive concentration in solution up to a specific threshold value, beyond which no benefit in terms of calcium scale inhibition is gained. Furthermore, interfacial tension has been computed without and with citric acid at 0.520 × 10−3 and 1.041 × 10−3 M, as a function of the different concentration amounts investigated. The values obtained are in good agreement with data reported in the literature.

In recent years, the discharge of various emerging pollutants, chemicals, and dyes in water and wastewater has represented one of the prominent human problems. Since water pollution is directly related to human health, highly resistant and emerging compounds in aquatic environments will pose many potential risks to the health of all living beings. Therefore, water pollution is a very acute problem that has constantly increased in recent years with the expansion of various industries. Consequently, choosing efficient and innovative wastewater treatment methods to remove contaminants is crucial. Among advanced oxidation processes, electrochemical oxidation (EO) is the most common and effective method for removing persistent pollutants from municipal and industrial wastewater. However, despite the great progress in using EO to treat real wastewater, there are still many gaps. This is due to the lack of comprehensive information on the operating parameters which affect the process and its operating costs. In this paper, among various scientific articles, the impact of operational parameters on the EO performances, a comparison between different electrochemical reactor configurations, and a report on general mechanisms of electrochemical oxidation of organic pollutants have been reported. Moreover, an evaluation of cost analysis and energy consumption requirements have also been discussed. Finally, the combination process between EO and photocatalysis (PC), called photoelectrocatalysis (PEC), has been discussed and reviewed briefly. This article shows that there is a direct relationship between important operating parameters with the amount of costs and the final removal efficiency of emerging pollutants. Optimal operating conditions can be achieved by paying special attention to reactor design, which can lead to higher efficiency and more efficient treatment. The rapid development of EO for removing emerging pollutants from impacted water and its combination with other green methods can result in more efficient approaches to face the pressing water pollution challenge. PEC proved to be a promising pollutants degradation technology, in which renewable energy sources can be adopted as a primer to perform an environmentally friendly water treatment.

Background Pressurised anaerobic digestion allows the production of biogas with a high content of methane and, at the same time, avoid the energy costs for the biogas upgrading and injection into the distribution grid. The technology carries potential, but the research faces practical constraints by a.o. the capital investment needed in high-pressure reactors and sensors and associated sampling limitations. In this work, the kinetic model of an autogenerative high-pressure anaerobic digestion of acetate, as the representative compound of the aceticlastic methanogenesis route, in batch configuration, is proposed to predict the dynamic performance of pressurised digesters and support future experimental work. The modelling of autogenerative high-pressure anaerobic digestion in batch configuration, which is not extensively studied and simulated in the present literature, was developed, calibrated, and validated by using experimental results available from the literature. Results Under high-pressure conditions, the assessment of the Monod maximum specific uptake rate, the half-saturation constant and the first-order decay rate was carried out, and the values of 5.9 kg COD kg COD−1 d−1, 0.05 kg COD m−3 and 0.02 d−1 were determined, respectively. By using the predicted values, excellent fittings of the final pressure, the CH4 molar fraction and the specific methanogenic yield calculation were obtained. Likewise, the variation in the gas–liquid mass transfer coefficient by several orders of magnitude showed negligible effects on the model predictive values in terms of methane molar fraction of the produced biogas, while the final pressure seemed to be slightly influenced. Conclusions The proposed model allowed to estimate the Monod maximum specific uptake rate for acetate, the half-saturation rate for acetate and the first-order decay rate constant, which were comparable with literature values reported for well-studied methanogens under anaerobic digestion at atmospheric pressure. The methane molar fraction and the final pressure predicted by the model showed different responses towards the variation of the gas–liquid mass transfer coefficient since the former seemed not to be affected by the variation of the gas–liquid mass transfer coefficient; in contrast, the final pressure seemed to be slightly influenced. The proposed approach may also allow to potentially identify the methanogens species able to be predominant at high pressure.

Microalgae biomass have been used as a source of nutrient-rich food, feed, and health-promoting compounds. Among the several commercially available microalgae, Haematococcus pluvialis is the most abundant source of natural astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4′-dione), which is considered as “super antioxidant.” Therefore natural astaxanthin produced by H. pluvialis has a higher antioxidant capacity than the synthetic sources, which reduces oxidative stress and free radicals and helps the human body to maintain a healthy state. However, H. pluvialis contains astaxanthin inside the cells, which need to be extracted using nontoxic extraction technologies for different application. Among the different available extraction technologies, supercritical fluid extraction (SFE) is a modern technology with increasing applications in pharmaceutical and nutraceutical sector. The most frequently employed supercritical solvent in food and natural product processing is carbon dioxide (CO2) due to its low critical temperature and pressure while considered as nontoxic extraction solvent. Therefore, nowadays, supercritical carbon dioxide (SC-CO2) is considered as a new substitute for complete extraction of natural compounds from different matrices. However, the extraction efficiency and purity of astaxanthin in the extract are influenced by different operative conditions such as the extraction pressure, temperature, time, and use of cosolvent. Hence the optimum operative condition of SC-CO2 extraction could enhance the extraction yields of astaxanthin and of its purity the extract. Therefore present chapter summarizes the effects of several extraction parameters on SC-CO2 extraction of astaxanthin from H. pluvialis, which could serve as benchmark for future development of SC-CO2 extraction technology and its commercial implementation in pharmaceutical and nutraceutical sector.

The uncontrolled carbon dioxide (CO2) emission is increasing every day due to human activities and the rapid industrial revolution. However, mainly oil-producing countries, and highly populated and industrialized countries, are the highest emitters of CO2. At present, CO2 concentration is approximately 408 ppm in the environment, which causes several ecological issues, like global warming, and disturbs the fauna and flora of the Earth. Therefore, many approaches (physical, chemical, and biological) are used to solve this major ecological threat and reduce CO2 concentration in the ecosystem. Among the available approaches, biological CO2 mitigation process is more feasible as compared to physical and chemical approaches due to low cost and zero emission of other pollutants. Mainly, plants, cyanobacteria, and microalgae generally fix CO2 from the atmosphere and utilize it as a carbon source for their growth. Recently, microalgal cultivation has gained tremendous research interest worldwide, due to their high growth rates, higher CO2 sequestration rate, and the accumulation of high-value-added compounds during the growth phase. Moreover, microalgal-based CO2 sequestering system can be developed at the industrial sites. The microalgal sequestering system is considered as a green technology for capturing CO2 from the industrial flue gases exhaust for biomass production. Moreover, the biomass of microalgae can be utilized in nutraceuticals, cosmetic and energy sectors, which can improve the economic viability of microalgal-based CO2 mitigation process. Thus, this chapter discusses the microalgal-based system for atmospheric CO2 capture and the application of algal biomass to improve the economic viability.

The main purpose of this study is to investigate the effects of operative parameters and bioprocess strategies on the photo-autotrophic cultivation of the microalgae Scenedesmus almeriensis for lutein production. S. almeriensis was cultivated in a vertical bubble column photobioreactor (VBC-PBR) in batch mode and the bioactive compounds were extracted by accelerated solvent extraction with ethanol at 67°C and 10 MPa. The cultivation with a volume fraction of CO2 in the range 0–3.0%v/v showed that the highest biomass and lutein concentrations – 3.7 g/L and 5.71 mg/g, respectively – were measured at the highest CO2 concentration and using fresh growth medium. Recycling the cultivation medium from harvested microalgae resulted in decreased biomass and lutein content. The nutrient chemical composition analysis showed the highest consumption rates for nitrogen and phosphorus, with values higher than 80%, while sulfate and chloride were less consumed.

The positioning of quality detection points as well as the frequency of sampling is a crucial aspect for the implementation of Water Safety Plans (WSPs), which have been proposed worldwide to ensure water quality and to minimize the risk from contamination in water distribution networks (WDNs). In this regard, some international legislations and best practices about quality of drinking water suggest very fine sampling frequencies, but they do not specify where the detection points should be located in a WDN. In this paper, three different approaches, based on empiricism, optimization and topology, respectively, were applied to locate detection quality points in a WDN. The comparison highlighted that empirical approach commonly adopted by water utility practitioners is unsatisfactory. The optimization-based approach, although performing significantly better, is difficult to apply, since it requires a calibrated hydraulic model. The topological approach, based on the use of the betweenness centrality and not requiring any hydraulic information and simulation, proves to be effective, and it can be easily adopted by water utilities to identify the location for quality detection points, due to its simplicity compared with the optimization-based approach.

The sorption of some benzene derivatives: o-xylene, toluene, phenol, benzyl alcohol, resorcinol and hydroquinone onto a zeolitic tuff-humic acid adduct (PCT-ImHA) was analysed by batch technique at 25°C and neutral pH. PCT-ImHA was prepared by binding leonardite-extracted humic acids (HA) to a zeolitic tuff sample rich in phillipsite and chabazite and enriched with Ca2+by cation exchange (Ca-PCT). The HA calcium salts were gently mixed with wet Ca-PCT; then, the mixture was heated at 330°C for 1.5h. An adduct with almost 2% of HA was obtained. The experimental data were well fitted by the Langmuir adsorption isotherm and showed that saturation capacity (qMax) increased with the octanol-water repartition coefficient (KO-W). The comparison with previous data on sorption onto immobilised HA highlights that qMaxvalues for PCT-ImHA are far higher than the sum of the contributions of the two separate components.

Microalgae are among the most interesting eukaryotic photosynthethic microorganisms able to use solar energy, nutrients and carbon dioxide to convert them into proteins, carbohydrates, lipids and other valuable organic compounds including carotenoids. Astaxanthin is one of the most interesting antioxidant molecules which has attracted crescent interest due to its positive effects on health and the numerous applications in different sectors, from nutraceutical to cosmetic and aquaculture. Even though the astaxanthin properties are well-known, its price still remains high if associated to the algal form, exceeding ~6000 Eur/Kg. This can be explained by considering the process expenses related to the extraction and purification steps of microalga intracellular metabolites. In fact, the downstream stage of this biotechnological process often accounts for more than 60–70% of total production costs. Optimized extraction and purification operations might contribute to microalgae market with the advantage to commercialize a natural existing astaxanthin form. The aim of this paper is the evaluation of the use of commercial activated carbon Darco™ G-60 for the purification of astaxanthin from an extraction broth. Astaxanthin was firstly extracted from Haematococcus pluvialis red phase supplied by Micoperi Blue Growth, an Italian Company that is working for a long time and it is specialized in the microalgae growth. Extraction was performed by Accelerated Solvent Extractor (ASE®200 DIONEX) at 100 bar and 67°C by using ethanol as green solvent with the main advantage to separate all the unipolar fractions as well as insoluble fractions from astaxanthin extracts (fibers, carbohydrate, ashes). In the second step, astaxanthin was purified with a column filled with activated carbon. Experimental tests by changing the mass of activated carbon were carried out (50mg, 100mg and 200mg)and with a flow rate in the range 0.9-1.0ml/min. All the experimental tests were carried out at room temperature (20°C). Results showed that by using activated carbon, it is possible to obtain an adsorption capacity of DARCO G60 in the range 21,9-23,9 mg/g.

Agro-industrial waste (AW) could be attractive carbon (C) source that have potential for production of high value-added biopolymers. AW can be derived from different sectors based on the compositional variation and transformed into biopolymers. Biopolymers are synthesized from diverse group of microbes and can be categorized into different groups. These biopolymers are a storing compound that is available in the cytoplasm of different group of microorganisms. This chapter describes the potential of AW for production of biopolymers, which allows the conversion of organic AW into biodegradable polymer production using the ecobiotechnological approach to reduce the overall cost. This will allow the development of the low-cost biopolymers, which can have different applications in various sectors. Therefore, it will increase demand of sustainable products with the rising its market demand.

Lutein has several benefits for human health, playing an important role in the prevention of age-related macular degeneration (AMD), cataracts, amelioration of the first stages of atherosclerosis, and some types of cancer. In this work, the Scenedesmus almeriensis microalga was used as a natural source for the supercritical fluid (SF) extraction of lutein. For this purpose, the optimization of the main parameters affecting the extraction, such as biomass pre-treatment, temperature, pressure, and carbon dioxide (CO2) flow rate, was performed. In the first stage, the effect of mechanical pre-treatment (diatomaceous earth (DE) and biomass mixing in the range 0.25–1 DE/biomass; grinding speed varying between 0 and 600 rpm, and pre-treatment time changing from 2.5 to 10 min), was evaluated on lutein extraction efficiency. In the second stage, the influence of SF-CO2 extraction parameters such as pressure (25–55 MPa), temperature (50 and 65 °C), and CO2 flow rate (7.24 and 14.48 g/min) on lutein recovery and purity was investigated. The results demonstrated that by increasing temperature, pressure, and CO2 flow rate lutein recovery and purity were improved. The maximum lutein recovery (~98%) with purity of ~34% was achieved operating at 65 °C and 55 MPa with a CO2 flow rate of 14.48 g/min. Therefore, optimum conditions could be useful in food industries for lutein supplementation in food products.

The removal of groundwater contamination is a complex process due to the hydro-geochemical characteristics of the specific site, related maintenance and the possible presence of several types of pollutants, both organic and inorganic. In recent decades, there has been an increasing drive towards more sustainable treatment for contaminated groundwater as opposed to “intensive” treatments, i.e. with high requirements for onsite infrastructure, energy and resource use. In this study, a new remediation technology is proposed, combining the use of advanced drainage systems with adsorption processes, termed “In-situ reactive DRAINage system for groundwater TREATment” (In-DRAIN-TREAT). By taking advantage of the groundwater natural gradient, In-DRAIN-TREAT collects the contaminated groundwater via a drainage system and treats the polluted water directly into an active cell located downstream, avoiding external energy inputs. Preliminary results indicate the applicability and high efficiency of In-DRAIN-TREAT when compared with a permeable reactive barrier (PRB). In-DRAIN-TREAT is applied to remediate a theoretical aquifer with low permeability, contaminated by a 13 m wide hexavalent chromium (CrVI) plume. This is achieved in less than a year, via a drain DN500, 32 m long, a 30 m3 treatment cell filled with activated carbon and no energy consumption. A comparison with permeable barriers also shows a preliminary 63% volume reduction, with a related 10% decrease of remediation costs.

In this paper, the activity of a cobalt/molybdenum (Co/Mo) commercial catalyst for the Water Gas Shift Reaction for hydrogen production was investigated in a three fixed-bed reactor pilot plant using a tar-rich synthesis gas from a full-scale biomass gasification plant as feed-stream. A parametric variation study was carried out to assess CO conversion (X CO ) and selectivity for the water gas shift reaction as a function of the operating temperature (T) in the range 300–450 °C. The effects of four dry gas hourly space velocities (GHSV), Case A-Case D, two steam to dry synthesis gas ratios (H 2 O/SG), 56% v/v and 67% v/v, and a H 2 S concentration in the range 100–220 ppm v,db were investigated: the highest CO conversion (∼95%) was observed in the base case (Case A GHSV) at 67% v/v H 2 O/SG, and 450 °C, the lower the operating temperature the lower the CO concentration, the lower the gas hourly space velocity the higher the CO conversion and the higher the H 2 O/SG the higher the CO conversion. The effect of H 2 S variation on CO conversion was also studied, keeping the operating temperature constant (≈365 °C) and using the Case D GHSV: CO conversion increased as the H 2 S concentration increased and X CO ≈ 40%. Selectivity was not influenced by the parameters investigated. Finally, the effect of the catalyst on tar removal was studied and a CO conversion close to 85% was found.

The advanced treatment of polluted liquid streams containing traces of pharmaceutical compounds is a major issue, since more and more effluents from pharma labs and wastewaters containing the excretions of medically treated humans and animals are discharged in the conventional wastewater treatment plants without previous effective treatments. Ibuprofen is a widely used non-steroidal anti-inflammatory drug (NSAID), which explains why it is found in wastewaters so often. In this paper, the removal of IBP from simulated water streams was investigated by using a lab-scale experimental device, consisting of a batch reactor equipped with a lamp emitting monochromatic UV light at a fixed wavelength (254 nm) and various intensities. Three sets of experiments were carried out: the first to study IBP concentration as a function of time, at different volumes of treated solutions (V = 10–30 mL); the second to explore the effect of pH on IBP degradation as a function of time (pH = 2.25–8.25) and the third to evaluate the effect of different UV light intensities on IBP degradation (E = 100–400 mJ m−2). The IBP initial concentration (IBP 0) was varied in the range 30–60 mg L−1. The results obtained show that the concentration of IBP decreases along with treatment time, with a negative effect of the treated volume, i.e. smaller volumes, such as lower liquid heights, are more easily degraded. Moreover, the higher the pH, the better the IBP degradation; actually, when pH increases from 2.25 to 6.6 and 8.25, the IBP concentration, after an hour of treatment, decreases respectively to 45, 34 and 27 % of its initial value. In addition, as the intensity of light increases from 100 to 400 mJ m−2, the IBP concentration decreases to 34 % of its initial value. A reaction scheme is put forward in the paper, which well describes the effects of volume, pH and light intensity on the IBP degradation measured experimentally. Moreover, the IBP degradation by-products have been identified.

The aim of this study is to describe the synthetic procedure of superparamagnetic nanoparticles of magnetite and maghemite and to use the magnetic merit of thesenano-sized ferrite particles coated byorganic substances having good water solubility to desalinate saline water. The idea derives from the experimental results of research groups using magnetic particles covered by polymers to increase the efficiency of membranes in forward osmosis desalination plants. The magnetic particles can beseparatedfrom water by an external magnet field easily.As magnetic particles, Fe3O4 can be prepared in different sizes from nanoto microscale by the help of co-precipitation or thermal decomposition techniques. These superparamagnetic nanoparticles are well-promising candidates for use in desalination purposes either from own or after their fabrication with polymer molecules, such as cyclodexrins, in their original form or in a modified one in order to enhance their water solubility, according to some preliminary experimental results found by our research team but not referred here. Herein, various inexpensive synthetic routes for superparamagnetic nanoparticles of magnetite (Fe3O4) and maghemite ( -Fe2O3) are described, as well as the characterization results of the produced nanoparticles with XRD, TEM, FT-IR, RAMAN, DFT and TGA/DTG analytical techniques are also referred.

Hexavalent chromium (Cr(VI)) in water systems is a major hazard for living organisms, including humans. The most popular technology currently used to remove Cr(VI) from polluted water is sorption for its effectiveness, ease of use, low cost and environmental friendliness. The electrostatic interactions between chromium species and the sorbent matrix are the main determinants of Cr(VI) sorption. The pH plays a central role in the process by affecting chromium speciation and the net charge on sorbent surface. In most cases, Cr(VI) sorption is an endothermic process whose kinetics is satisfactorily described by the pseudo second-order model. A critical survey of the recent literature, however, reveals that the thermodynamic and kinetic parameters reported for Cr(VI) sorption are often incorrect and/or erroneously interpreted.

The molecular structure of a commercial sample of humic acids (HA) was investigated by membrane dialysis experiments (MD) and low-pressure size-exclusion chromatography (LP-SEC). MD showed that HA molecules were retained by dialysis membrane with a cut-off of 6&ndash, 8 kDa, independently from HA concentration (15 or 150 mg L&minus, 1), NaHCO3 concentration (0.005&ndash, 2.0 mol L&minus, 1), and from propan 2-ol (0&ndash, 5 v/v %). SEC experiments at low pressure gave chromatograms with a broad peak, with an elution volume between those of the globular proteins bovine serum albumin (molecular weight = 66.5 kDa) and lysozyme from egg (molecular weight = 14.4 kDa). The pattern of the chromatogram did not vary with HA concentration, and second-run chromatograms of single eluted fractions showed relatively sharp peaks. From these data, we reveal that the commercial HA sample analysed has a macromolecular structure rather than being a supramolecular aggregate of relatively small molecules, as recently proposed for some samples of HA obtained from different sources.

This research shows that carbon dioxide supercritical fluid (CO2-SF) is an emerging technology for the extraction of high interest compounds for applications in the manufacturing of pharmaceuticals, nutraceuticals, and cosmetics from microalgae. The purpose of this study is to recover fatty acids (FAs) and, more precisely, eicosapentaenoic acid (EPA) from Nannochloropsis gaditana biomass by CO2-SF extraction. In the paper, the effect of mechanical pre-treatment was evaluated with the aim of increasing FAs recovery. Extraction was performed at a pressure range of 250–550 bars and a CO2 flow rate of 7.24 and 14.48 g/min, while temperature was fixed at 50 or 65 °C. The effect of these parameters on the extraction yield was assessed at each extraction cycle, 20 min each, for a total extraction time of 100 min. Furthermore, the effect of biomass loading on EPA recovery was evaluated. The highest EPA extraction yield, i.e., 11.50 mg/g, corresponding to 27.4% EPA recovery, was obtained at 65 °C and 250 bars with a CO2 flow rate of 7.24 g/min and 1.0 g biomass loading. The increased CO2 flow rate from 7.24 to 14.48 g/min enhanced the cumulative EPA recovery at 250 bars. The purity of EPA could be improved by biomass loading of 2.01 g, even if recovery was reduced.

In the last decades the interest in the biomass gasification process has increased due to the growing attention to the use of sustainable energy. Biomass is a renewable energy source and represents a valid alternative to fossil fuels. Gasification is the thermochemical conversion of an organic material into a valuable gaseous product, called syngas, and a solid product, called char. The biomass gasification represents an efficient process for the production of power and heat and the production of hydrogen and second-generation biofuels. This paper deals with the state of the art biomass gasification technologies, evaluating advantages and disadvantages, the potential use of the syngas and the application of the biomass gasification. Syngas cleaning though fundamental to evaluate any gasification technology is not included in this paper since; in the authors' opinion, a dedicated review is necessary. © 2015 Science Press and Dalian Institute of Chemical Physics.

Water network partitioning (WNP) concerns the implementation of the paradigm of ‘divide and conquer’ in the water supply systems consisting in dividing a water network into k smaller subsystems by gate valves and flow meters. WNP allows improving the management of water distribution systems by transforming into Smart WAter Networks (SWANs) that represent key subsystems of Smart Cities. WNP is possible if water utilities start to use isolating valves (also with control devices) and flow meters. These instruments open new perspectives for the management of water supply systems both in terms of water saving and water protection. Recently, starting from the advantages offered by computing power and network analysis tools, some techniques based on graph partitioning algorithms have been developed by the authors to improve water management and protection, implementing the paradigm of ‘divide and conquer’. This paper presents the second release of SWANP 2.0 (Smart WAter Network Partitioning and Protection) software that integrates two different algorithms, based on multilevel and multi-agent techniques, for WNP and a novel algorithm, based on a multi-objective function, for water network protection from intentional contamination. The SWANP 2.0 software, developed in Python v2.7.6 language, provides the decision-maker different solutions comparing network layouts with some hydraulic and protection performance indices.

This paper presents an experimental study of the ultrasonic degradation of organic pollutants in terms of the effect of ultrasonic frequency (40–380–850–1000 kHz). The removal efficiency of two endocrine disrupting compounds [17β-estradiol (E2) and 17α-ethinylestradiol (EE2)] is investigated using laboratory scale ultrasonic baths at low power intensities. Higher ultrasonic frequencies were found to be more effective for pollutant degradation with 850 kHz the best: 9.0 × 10−1 mg/kW h for E2 and 6.8 × 10−1 mg/kW h for EE2 at initial concentrations of 1 ppm. Additionally, the removal of p-nitrophenol was investigated under the same conditions, as a dosimetry reaction for estimating the hydroxyl radical production, key component in organic pollutant removal. In order to describe the overall phenomena occurring inside the reactor and to predict the apparent hydroxyl radical production, a simulation algorithm is proposed. It incorporates the solution of ODE systems that embodies bubble dynamics, heat and mass transfer through the bubble wall and chemical reactions in the gas–vapor phase for an initial bubble nuclei population. The experimental degradation measures of p-nitrophenol over the range of frequencies studied were found to be comparable with the model results of hydroxyl radicals produced during the sonication treatment.

Solvent Extraction was tested to extract astaxanthin from Haematococcus pluvialis in red phase (HPR), by investigating effects of solvents, extraction pressure and temperature. Astaxanthin isomers were identified and quantified in the extract. The performances of acetone and ethanol, Generally Recognized As Safe (GRAS) solvents, were explored. Negligible effect of pressure was found, while with increasing extraction temperature astaxanthin recovery increased till a maximum value, beyond which thermal degradation seemed to be greater than the positive effect of temperature on extraction. Furthermore, to maximize the extraction yield of astaxanthin, mechanical pre-treatment of HPR biomass was carried out and several extraction runs were consecutively performed. Experimental results showed that after the mechanical pre-treatment the astaxanthin recovery strongly increased while a single extraction run of 20 min was sufficient to extract more than 99% of total astaxanthin extracted. After pre-treatment, maximum recovery of about 87% was found for acetone (pressure = 100 bar; temperature = 40 °C; total time = 60 min).

In this work, the results of equilibrium and dynamic adsorption tests of hexavalent chromium, Cr (VI), on activated carbon are presented. Adsorption isotherms were determined at different levels of pH and temperature. Dynamic tests were carried out in terms of breakthrough curves of lab-scale fixed bed column at different pH, inlet concentration and flow rate. Both the adsorption isotherms and the breakthrough curves showed non-linear and unconventional trends. The experimental results revealed that chromium speciation played a key role in the adsorption process, also for the occurrence of Cr(VI)-to-Cr(III) reduction reactions. Equilibrium tests were interpreted in light of a multi-component Langmuir model supported by ion speciation analysis. For the interpretation of the adsorption dynamic tests, a mass transfer model was proposed.Dynamic tests at pH 11 were well described considering the external mass transfer as the rate controlling step. Differently, for dynamic tests at pH 6 the same model provided a satisfying description of the experimental breakthrough curves only until a sorbent coverage around 1.6mgg-1. Above this level, a marked reduction of the breakthrough curve slope was observed in response to a transition to an inter-particle adsorption mechanism. © 2014 Elsevier B.V.

Humic acids (HA) are promising green materials for water and wastewater treatment. They show a strong ability to sorb cationic and hydrophobic organic pollutants. Cationic compounds interact mainly by electrostatic interaction with the deprotonated carboxylic groups of HA. Other functional groups of HA such as quinones, may form covalent bonds with aromatic ammines or similar organic compounds. Computational and experimental works show that the interaction of HA with hydrophobic organics is mainly due to π–π interactions, hydrophobic effect and hydrogen bonding. Several works report that sorbing efficiency is related to the hydrophobicity of the sorbate. Papers about the interaction between organic pollutants and humic acids dissolved in solution, in the solid state and adsorbed onto solid particles, like aluminosilicates and magnetic materials, are reviewed and discussed. A short discussion of the thermodynamics and kinetics of the sorption process, with indication of the main mistakes reported in literature, is also given.

In this paper, a Permeable Reactive Barrier (PRB) made with activated carbon, namely a Permeable Adsorptive Barrier (PAB), is put forward as an effective technique for the remediation of aquifers simultaneously contaminated by some chlorinated organic compounds. A design procedure, based on a computer code and including different routines, is presented as a tool to accurately describe mass transport within the aquifer and adsorption/desorption phenomena occurring inside the barrier. The remediation of a contaminated aquifer near a solid waste landfill in the district of Napoli (Italy), where Tetrachloroethylene (PCE) and Trichloroethylene (TCE) are simultaneously present, is considered as a case study. A complete hydrological and geotechnical site characterization, as well as a number of dedicated adsorption laboratory tests for the determination of activated carbon PCE/TCE adsorption capacity in binary systems, are carried out to support the barrier design. By means of a series of numerical simulations it is possible to determine the optimal barrier location, orientation and dimensions. PABs appear to be an effective remediation tool for the in-situ treatment of an aquifer contaminated by PCE and TCE simultaneously, as the concentration of both compounds flowing out of the barrier is everywhere lower than the regulatory limits on groundwater quality.

The chemical effect of hydrodynamic cavitation (HC) in a Venturi reactor from both the theoretical and the experimental point of view is dealt. A mathematical model is presented to simulate the global production of hydroxyl radicals; it is based on a set of ordinary differential equations that account for the hydrodynamics, mass diffusion, heat exchange, and chemical reactions inside the bubbles. Experimentally, the degradation of p-nitrophenol (initial concentration 0.15 g dm−3) has been conducted in a lab scale Venturi reactor at inlet pressure ranging from 0.2 to 0.6 MPa and has been used to estimate the hydroxyl radical production. The optimum configuration, suggested by numerical simulations, has been experimentally confirmed. Thanks to the empirical validation, this novel modeling approach can be considered as a theoretical tool to identify the best configuration of HC operating parameters. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2566–2572, 2014

Lutein has several benefits for human health, playing an important role in the prevention of age-related macular degeneration (AMD), cataracts, amelioration of the first stages of atherosclerosis, and some types of cancer. In this work, the Scenedesmus almeriensis microalga was used as a natural source for the supercritical fluid (SF) extraction of lutein. For this purpose, the optimization of the main parameters affecting the extraction, such as biomass pre-treatment, temperature, pressure, and carbon dioxide (CO2) flow rate, was performed. In the first stage, the effect of mechanical pre-treatment (diatomaceous earth (DE) and biomass mixing in the range 0.25&ndash, 1 DE/biomass, grinding speed varying between 0 and 600 rpm, and pre-treatment time changing from 2.5 to 10 min), was evaluated on lutein extraction efficiency. In the second stage, the influence of SF-CO2 extraction parameters such as pressure (25&ndash, 55 MPa), temperature (50 and 65 &deg, C), and CO2 flow rate (7.24 and 14.48 g/min) on lutein recovery and purity was investigated. The results demonstrated that by increasing temperature, pressure, and CO2 flow rate lutein recovery and purity were improved. The maximum lutein recovery (~98%) with purity of ~34% was achieved operating at 65 &deg, C and 55 MPa with a CO2 flow rate of 14.48 g/min. Therefore, optimum conditions could be useful in food industries for lutein supplementation in food products.

The introduction of cyanide with a backflow attack into a water system was studied. The recent development of techniques for water network sectorization, aimed to improve the management of water systems, represents also an efficient way to protect networks from intentional contamination. The possibility of closing gate valves by a remote control system to create an i-DMA (isolated District Meter Area) can reduce the risk of contamination and thus the extent of damage of a terroristic attack. The study proposes a novel technique for designing i-DMAs compatible with hydraulic performance and optimized for water network protection.

In this work, an experimental and modeling analysis of the adsorption of four aromatic compounds (i.e., toluene, naphthalene, o-xylene and ethylbenzene) onto a commercial activated carbon is carried out. The aim is to assess the suitability of the adsorption process for the treatment of polluted groundwater, also when a multiple contamination is detected. Batch adsorption tests from simulated polluted groundwater are performed in single-compound systems and in two binary systems (i.e., toluene + naphthalene and o-xylene + ethylbenzene), at constant temperature (20°C) and pH (7). Experimental results in single-compound systems reveal that all of the analytes are significantly adsorbed on the tested activated carbon. In particular, toluene and naphthalene adsorption capacities are the highest and of similar value, while for o-xylene and ethylbenzene, the performances are lower. The adsorption of these compounds seems to be influenced by a combined effect of several parameters, such as hydrophobicity, molecule size, structure of the molecule, etc. Experimental results in binary systems show a different behavior of the two systems, which confirms their complexity and explains the interest in these complex adsorption systems. In particular, toluene and naphthalene are mutually competitive, while in the case of o-xylene + ethylbenzene, only the former undergoes competitive effects. The analysis of the entire experimental data set is integrated with a dedicated modeling analysis using the extended Langmuir model. For both single-compound and binary systems, this model provides acceptable results, in particular for low equilibrium concentrations, like those more commonly found in groundwater, and for the compounds involved in adsorptive competitive effects. © 2014 by the authors.

"This paper presents a theoretical study of cavitation as an advanced oxidation process. A. mathematical algorithm, which couples single bubble dynamics and chemical reactions for a. cavitating bubble, is proposed and compared with experimental and theoretical works. reported in the literature. The main output variable, used for comparison, is the hydroxyl. radical production. A wide range of parameter values is evaluated for the analysis of hydro-. dynamic cavitation in an orifice. Thanks to the large number of simulation, it was possible to. find a very good agreement with a design correlation proposed in the literature. Addition-. ally, a novel approach has been proposed, which consists of integrating the estimated radical. production over a typical bubble size distribution in order to predict a global oxidant pro-. duction. Moreover, by fixing the values of flowrate, pressure, and geometric parameters, a. real experimental condition of hydrodynamic cavitation in a Venturi device has been simu-. lated. This allowed the comparison of simulation results with the experimental ones reported. in the literature. A good agreement has been found in terms of cavitational yield, an estima-. tion of the process efficiency from an energetic perspective."

"Each single phase of a water supply network, from water adduction to distribution. to end-users, is exposed to many diverse potential sources of intentional contamination (or. malicious attacks). One of the most dangerous threats is a backflow attack that occurs when. a pump system, easily available on the market, is utilized to overcome the pressure gradient. of network pipes. In this work, a simple backflow attack with cyanide being introduced into. a real-water system is modeled and the most dangerous introduction points for a contaminant. incident are defined. Moreover, the network vulnerability has been analyzed by computing. the lethal dose of cyanide ingested by users and the total length of the contaminated water. system. Eventually the effects of network partitioning and district isolation to protect water. supply systems have been investigated. The results show how district closing - by network. sectorization techniques used to improve leakage search and reduction - can significantly. decrease contaminant diffusion and protect part of the users from cyanide uptake. Network. sectorization can also reduce the risk of simple malicious attacks because several. introduction points are necessary to have a massive negative impact on the network.. Simulation results also show that in some cases water network partitioning may worsen water. network protection and further studies are necessary to design water districts for network security and safety."

Microalgae Dunaliella salina contains useful molecules such as &beta, carotene and fatty acids (FAs), which are considered high value-added compounds. To extract these molecules, supercritical carbon dioxide was used at different operative conditions. The effects of mechanical pre-treatment (grinding speed at 0&ndash, 600 rpm, pre-treatment time of 2.5&ndash, 7.5 min) and operating parameters for extraction, such as biomass loading (2.45 and 7.53 g), pressure (100&ndash, 550 bars), temperature (50&ndash, 75 &deg, C) and CO2 flow rate (7.24 and 14.48 g/min) by varying the extraction times (30&ndash, 110 min) were evaluated. Results showed that the maximum cumulative recovery (25.48%) of &beta, carotene was achieved at 400 bars and 65 &deg, C with a CO2 flow rate of 14.48 g/min, while the highest purity for stage (55.40%) was attained at 550 bars and 65 &deg, C with a CO2 flow rate of 14.48 g/min. The maximum recovery of FAs, equal to 8.47 mg/g, was achieved at 550 bars and 75 &deg, C with a CO2 flow rate of 14.48 g/min. Moreover, the lowest biomass loading (2.45 g) and the first extraction cycle (30 min) allowed the maximum extraction of &beta, carotene and FAs.

This work presents the development of novel multifunctional Shape Memory Alloy (SMA) coatings aiming to improve the mechanical behavior of structural components, as well as their corrosion resistance. The groundbreaking concept of the new coating material is described briefly as follows: Upon heating, the SMA coating tends to recover its experienced deformation and return to its original shape. At that point, shear forces developing at the interface between coating and structure are expected to mitigate the deformation of the structure and reduce its overall stress field level. The latter is a great benefit for regions where cracks exist, since the local reduction of the stress field will delay the crack propagation and hence the structural failure. Numerical analysis is performed to gain understanding of the expected thermomechanical response of the entire SMA-coated composite structure. The influence of the alloy composition and precipitates on the thermomechanical properties are also examined. The SMA coating is subjected to appropriate processing conditions and deposited on metallic substrates of proper geometry following a custom-designed two-phase process, which enables beneficial shape recovery enabling the efficient mitigation of the structure's deformation. Processing consists of aging heat treatments, which are of paramount importance for endowing the coating with the shape memory effect. The effect of heat treatment conditions on the thermo-mechanical fatigue response of the material was also characterized. The developed SMA coatings on aluminum structural elements can find significant application in aeronautical engineering, as for example in the aircraft wing box structure reinforcement and the fuselage structure to enhance their structural integrity.

In this work, an experimental study aimed at the assessment of the factors affecting the adsorption of trichloroethylene (TCE) from water solutions onto activated carbons is presented. The influence of sorbent properties, such as B.E.T. surface area, micropore volume, chemical composition and acid/basic surface functional groups on TCE adsorption capacity is experimentally assessed by testing a set of 12 sorbents. Moreover, the effect of the presence of other species in solution, such as sodium acetate and tetrachloroethylene (PCE), is studied through parametric TCE adsorption isotherms realization. The experimental results show that the TCE adsorption capacity is promoted by a high B.E.T. surface area, micropore volume and C content and it is significantly affected by the presence of a non-ionic compound of similar structure (PCE), however it does not depend on the presence of an organic salt (sodium acetate). These results confirm that neither TCE-carbon ionic interaction nor sorbent ionization phenomena are involved in the TCE adsorption, since its mechanism is based on dispersion forces (London-Van Der Walls interaction). A thorough analysis of the experimental data set suggests that, in consideration of the TCE adsorption mechanism, the maximization of basal plane extent (as the B.E.T. surface area) and its effective fraction (as the C content) is a valid criterion to select or synthesize a new suitable sorbent for TCE adsorption from waters. (C) 2009 Elsevier B.V. All rights reserved.

The production of biofuels from renewable sources is a major challenge in research. Methanol, ethanol, dimethyl ether (DME), synthetic natural gas (SNG), and hydrogen can be produced from syngas which is the result of the gasification of biomasses. Syngas composition varies according to the gasification technology used (such as fixed bed reactors, fluidized bed reactors, entrained flow reactors), the feedstock characteristics, and the operating parameters. This paper presents a review of the predominant biomass gasification technologies and biofuels obtained from syngas by biomass gasification. © 2018 by the authors.

This work studies the reliability of an activated carbon permeable reactive barrier in removing cadmium from a contaminated shallow aquifer. Laboratory tests have been performed to characterize the equilibrium and kinetic adsorption properties of the activated carbon in cadmium-containing aqueous solutions. A 2D numerical model has been used to describe pollutant transport within a groundwater and the pollutant adsorption on the permeable adsorbing barrier (PRB). In particular, it has been considered the case of a permeable adsorbing barrier (PAB) used to protect a river from a Cd(II) contaminated groundwater. Numerical results show that the PAB can achieve a long-term efficiency by preventing river pollution for several months.

The comprehension of the mechanisms of nucleation and growth that regulate the gypsum (calcium sulfate dihydrate) precipitation is fundamental to prevent scaling problems. The present paper reports measurements of the induction period for gypsum nucleation when citric acid is added in solution as an additive to retard scale formation. The supersaturation ratio was varied in the interval 2.3-6.0, the concentration of citric acid ranged from 0.01 to 0.30 g/L, while in all experiments the temperature was fixed to 25°C. The induction period values were compared to those previously obtained, by using the same experimental technique, in the absence of foreign ions in the mother liquor, showing that the citric acid has a strong retarding effect towards gypsum nucleation. La comprehension des mecanismes de nucleation et de croissance qui regulent la precipitation de gypse (dihydrate de sulfate de calcium) est fondamentale pour empecher les problemes d'encrassement. On presente dans cet article des mesures de la periode d'induction pour la nucleation de gypse lorsque de l'acide citrique est ajoute a la solution comme additif pour retarder la formation de tartre. On a fait varier le taux de sursaturation dans l'intervalle de 2,3-6,0, la concentration d'acide citrique entre 0,01 et 0,30 g/L, tandis que dans toutes les experiences la temperature a ete fixee a 25 °C. Les valeurs de periode d'induction sont comparees a celles obtenues anterieurement, avec la meme technique experimentale, en l'absence d'ions etrangers dans l'eau-mere, montrant que l'acide citrique exerce un fort effet de retardement dans la nucleation du gypse.