Papers by Alireza Saraeian
Serious environmental concerns regarding the use of fossil-based fuels have raised awareness rega... more Serious environmental concerns regarding the use of fossil-based fuels have raised awareness regarding the necessity of alternative clean fuels and energy carriers. Biodiesel is considered a clean, biodegradable, and non-toxic diesel substitute produced via the transesterification of triglycerides with an alcohol in the presence of a proper catalyst. After initial separation of the by-product (glycerol), the crude biodiesel needs to be purified to meet the standard specifications prior to marketing. The presence of impurities in the biodiesel not only significantly affects its engine performance but also complicates its handling and storage. Therefore, biodiesel purification is an essential step prior to marketing. Biodiesel purification methods can be classified based on the nature of the process into equilibrium-based, affinity-based, membrane-based, reaction-based, and solid-liquid separation processes. The main adverse properties of biodiesel – namely moisture absorption, corrosiveness, and high viscosity – primarily arise from the presence of oxygen. To address these issues, several upgrading techniques have been proposed, among which catalytic (hydro)deoxygenation using conventional hydrotreating catalysts, supported metallic materials, and most recently transition metals in various forms appear promising. Nevertheless, catalyst deactivation (via coking) and/or inadequacy of product yields necessitate further research. This paper provides a comprehensive overview on the techniques and methods used for biodiesel purification and upgrading.
A molybdenum oxide catalyst in a low pressure hydrogen atmosphere was used for the hydrodeoxygena... more A molybdenum oxide catalyst in a low pressure hydrogen atmosphere was used for the hydrodeoxygenation (HDO) of pulsed injections of cellulose pyrolysis model compounds to examine reaction products. Higher catalyst loadings (≥20 : 1 catalyst : cellulose injection) in the HDO reactor were found to preferentially produce alkanes, while at lower loadings (≤10 : 1 catalyst : cellulose injection) alkene selectivity was increased. However, as the amount of catalyst was decreased, the pyrolysis vapors were not completely deoxygenated. The HDO of monofunctional oxygenated C 4 compounds found hydroxyl groups to be the most readily reacted and ether linkages to be the most recalcitrant. In general, the reactivity towards deoxygenation of the tested oxygen-containing functional groups was observed to be C–OH > CvO > C–OC. Several cellulose pyrolysis model compounds were also tested, including methyl glyoxal, glycolaldehyde, furfural, 5-hydroxy-methylfurfural, and levoglucosan, and found the same general trend to occur, except for levoglucosan, which was totally reacted and did not yield any oxygenated low molecular weight compounds despite containing two ether linkages. Across the compounds, the general reaction pathway was observed to include carbonyl/ alcohol hydrogenation/dehydrogenation, deoxygenation, and alkene isomerization and hydrogenation.
Desalination and Water Treatment, 2015
In recent years, heavy metal pollution has increased as a result of industrial growth, especially... more In recent years, heavy metal pollution has increased as a result of industrial growth, especially in industries such as electroplating, mining, metal finishing, battery production, and welding. Among the heavy metals, one of the most hazardous is cadmium, which accumulates in the human body and causes cancer along with cardiovascular, neurological, and respiratory problems. Hence, it is crucial to sequester cadmium ions from industrial effluent before the contaminated effluent is discharged into the sewage system. There are several traditional treatment methods for removing heavy metals from aqueous effluents, including chemical precipitation, ion exchange, and membrane filtration. These techniques have high operational costs and require the continuous input of chemicals, so they are neither economical nor ecologically sustainable. Therefore, biosorption has gained significant attention as an effective alternative for sequestering toxic heavy metals. In this work, Sorghum X drummond...
Scarcity of clean water is a great dilemma today and needs better management. About 1.2 billion p... more Scarcity of clean water is a great dilemma today and needs better management. About 1.2 billion people are living in areas where water is physically scarce and also 1.6 billion encounter economic water shortage. Population growth, climate change, and inappropriate use of available resources are the chief factors that worsen the current condition. Given that the amount of water on the earth has remained quite constant over time, it is crucial to desalinate saline and brackish waters. However, cost and concentrate stream of desalination units are two major issues that have restricted expansion of inland water desalination technologies. The salinity of concentrate stream which is sent to disposals increases with each succeeding separation step and causes environmental issues resulting in confining practical deployment of desalination units. Cultivation of microalgae in concentrate disposal is a new method which could contribute to solving these problems inasmuch as microalgae have been...
RSC Adv., 2015
A new hybrid nanostructured sorbent ZnCl 2 -MCM-41, was synthesized by a post-synthesis method in... more A new hybrid nanostructured sorbent ZnCl 2 -MCM-41, was synthesized by a post-synthesis method in toluene as the solvent. To characterize the sorbent, a number of methods were applied, including X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Characterization demonstrated that the sorbent particles are of semi-spherical shape, nanostructured with a 754 m 2 g À1 surface area and a 2.86 nm pore diameter. The Pb(II) removal depended on several parameters, including the pH of solution, temperature, initial Pb(II) concentration, sorbent dosage, ionic strength, and the amount of ZnCl 2 loaded on the MCM-41 surface. The results showed that the pseudo-second-order model describes the kinetics of sorption better than the pseudo-first-order model. The adsorption continuously increased in the pH range of 2.0-7.0, beyond which the adsorption could not be carried out due to the precipitation of the metal ions. The adsorbent had a considerably high Langmuir monolayer capacity of 479 mg g À1 . The adsorption process was exothermic at ambient temperature and the computation of the parameters DG , DH , and DS indicated the interactions to be thermodynamically favorable.
Water scarcity is a major global concern: because of factors such as population growth, inappropr... more Water scarcity is a major global concern: because of factors such as population growth, inappropriate use of water resources, and climate change, clean freshwater resources are strictly limited. However, seawater and brackish waters are abundant. Therefore, desalination processes are used to produce freshwater from seawater and brackish water, helping to overcome the critical issue of freshwater shortages. The most commonly used desalination processes are membrane technologies, which are dominant because of their low cost, low energy consumption, compactness, and short installation period. There are several different types of membrane technology, but reverse osmosis (RO) systems are the most frequently used: about half of the world’s 16,000 desalination plants use RO systems. The appeal of RO systems comes from their ability to treat many types of feed water, their ease of maintenance, and the high-quality water they produce. However, compared to some other membrane technologies, RO...
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Papers by Alireza Saraeian