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.
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.
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.
•We study the degradation of p-nitrophenol in a Venturi reactor.•The optimal value of the operating pressure is addressed.•We study the intrinsic kinetics with a novel approach.•The effects of pH and ...initial concentration are evaluated.•Numerical simulations are coupled with experimental results.
This paper presents a theoretical and experimental study of cavitation as an advanced oxidation process. The degradation rate of p-nitrophenol (PNP) was experimentally investigated and used as an estimator of the sonochemical effect in hydrodynamic cavitation. The PNP initial concentration was varied in the range 0.1–1gL−1 and the pressure in the range 0.2–0.7MPa, with a corresponding flow rate of 3.5–6.9Lmin−1. In terms of removal rate and energy efficiency, an optimal inlet pressure value was found close to 0.4MPa and cavitation number of 0.25. The calculated first-order kinetic constant values show the existence of an optimal configuration: k=1.13×10−2min−1 at 0.45MPa with a value for the electrical energy per order EEO=66.7kWhm−3. Moreover, the kinetic data was purged from the influence of the experimental apparatus configuration, allowing for the evaluation of an intrinsic kinetic constant. The physical–chemical behavior of hydrodynamic cavitation is discussed on the basis of single bubble dynamics. The numerical simulations, at different inlet pressures, provided a good explanation of the values observed. Furthermore, a simple energy balance on cavitating bubbles, taking into account for the actual production of cavitating events, gave a further confirmation of the experimental trends.
This paper aims to propose an innovative breakthrough methodology for hydrogen production through water splitting over Fe3O4 pellet at low temperature (T = 250 °C; 290 °C; 310 °C). In order to ...achieve this goal, the effects of magnetic field (B = 0 mT; 25.4 mT; 35.1 mT; 48.3 mT) and of electric power (P = 5 W; 12 W; 20 W) on reactive medium performance were investigated. Results show that production of hydrogen was mainly influenced by electric power applied and magnetic field, since the higher the magnetic field and the electric power the higher the production of hydrogen, while the temperature showed a secondary effect; however, feasible production of hydrogen was achieved at a temperature close to 300 °C.
•An innovative methodology for hydrogen production through water splitting at low temperature•Effects of the main operative parameters: temperature, magnetic field, electric power•The production of hydrogen is mainly influenced by electric power applied and magnetic field.•The temperature showed a secondary effect on hydrogen production.•Feasible production of hydrogen is achieved at a temperature close to 300 °C.
•Astaxanthin extraction by using Accelerated solvent extraction technology.•Extraction of bio-products from microalgae.•Effect of pretreatment on the yield extraction.
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 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.
Astaxanthin and lutein, antioxidants used in nutraceutics and cosmetics, can be extracted from several microalgal species. In this work, investigations on astaxanthin and lutein extraction from
(
) ...in the red phase were carried out by means of the supercritical fluid extraction (SFE) technique, in which CO₂ supercritical fluid was used as the extracting solvent with ethanol as the co-solvent. The experimental activity was performed using a bench-scale reactor in semi-batch configuration with varying extraction times (20, 40, 60, and 80 min), temperatures (50, 65, and 80 °C) and pressures (100, 400, and 550 bar). Moreover, the performance of CO₂ SFE with ethanol was compared to that without ethanol. The results show that the highest astaxanthin and lutein recoveries were found at 65 °C and 550 bar, with ~18.5 mg/g dry weight (~92%) astaxanthin and ~7.15 mg/g dry weight (~93%) lutein. The highest astaxanthin purity and the highest lutein purity were found at 80 °C and 400 bar, and at 65 °C and 550 bar, respectively.
In the last few years, many industrial sectors have generated and discharged large volumes of saline wastewater into the environment. In the present work, the electrochemical removal of nitrogen ...compounds from synthetic saline wastewater was investigated through a lab-scale experimental reactor. Experiments were carried out to examine the impacts of the operational parameters, such as electrolyte composition and concentration, applied current intensity, and initial ammoniacal nitrogen concentration, on the total nitrogen removal efficiency. Using NaCl as an electrolyte, the
removal was higher than Na
SO
and NaClO
; however, increasing the initial NaCl concentration over 250 mg·L
resulted in no benefits for the
removal efficiency. A rise in the current intensity from 0.05 A to 0.15 A resulted in an improvement in
removal. Nevertheless, a further increase to 0.25 A led to basically no enhancement of the efficiency. A lower initial ammoniacal nitrogen concentration resulted in higher removal efficiency. The highest
removal (about 75%) was achieved after 90 min of treatment operating with a NaCl concentration of 250 mg·L
at an applied current intensity of 0.15 A and with an initial ammoniacal nitrogen concentration of 13 mg·L
. The nitrogen degradation mechanism proposed assumes a series-parallel reaction system, with a first step in which NH
is in equilibrium with NH
. Moreover, the nitrogen molar balance showed that the main product of nitrogen oxidation was N
, but NO
was also detected. Collectively, electrochemical treatment is a promising approach for the removal of nitrogen compounds from impacted saline wastewater.
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.
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