Periodica Polytechnica Chemical Engineering

Facile Preparation of Bimetallic MOF-derived Supported Tungstophosphoric Acid Composites for Biodiesel Production

2023-02-14T12:07:20+00:00

In this work, the novel TPA@C-NiZr-MOF catalyst is synthesized by the impregnation of tungstophosphoric acid (TPA) on the NiZr-based metal-organic framework (NiZr-MOF) followed by calcination up to 300 °C. The as-prepared catalyst materials were structurally, morphologically, and texturally characterized by XRD, FTIR, temperature programmed desorption of NH₃ ( TPD-NH₃ ), N₂ physisorption, SEM, TEM, and XPS. The prepared catalyst can be used as an efficient heterogeneous catalyst for biodiesel production from oleic acid (OA) with methanol. The results indicated that, in comparison to TPA@NiZr-MOF, the TPA@C-NiZr-MOF catalyst calcined at 300 °C exhibits excellent catalytic performance probably owing to the synergistic effect between TPA and metal oxide skeletons, high acidity, as well as larger surface area and pore size. Additionally, the TPA@C-NiZr-MOF catalyst can be reused in up to six cycles with an acceptable conversion. This study showed that the bimetallic MOF-derived composite materials can be used as an alternative potential heterogeneous catalyst toward biorefinery applications.

The Effect of Microwave Irradiation on the Synthesis of Graphene from Battery Waste on Capacitance Properties

2023-01-06T09:08:40+00:00

Supercapacitor material is an alternative in energy storage. Supercapacitors are charge storage devices that have a high energy density, fast charge/discharge rates, long service life, wide operating temperature range, and are environmentally friendly. Graphene is a nanomaterial that can be used as a supercapacitor because it has high conductivity and a large surface area, but graphene can experience agglomeration so it can affect its capacitance properties. The microwave-assisted method can be used in the synthesis of graphene. Several microwave-based techniques are becoming more popular for producing graphene and altering it. Due to its quick, precise, uniform, and volumetric heating, microwave heating is a promising method for the thermochemical treatment and reduction of graphene oxide to graphene. This research aimed to examine the effect of microwave irradiation time on the capacitive properties of graphene synthesis as a supercapacitor. Graphene oxide (GO) can be reduced into graphene quickly and easily using microwave pulses lasting 15 to 30minutes to produce high-quality graphene fabrication. The characterization test was performed using UV-Vis, FTIR, SEM-EDX and cyclic voltammetry (CV). As a result, the optimum time is 25 minutes, and it showed an absorption peak at the 282 nm wavelength dan the CV analysis showed that the graphene has double capacitor properties with a specific capacitance of 140.7 F/g in 20 mV/s. Besides, the result of SEM indicated that graphene could be formed successfully. Its potential applications are also illustrated by emphasizing its usage as electrode material. Finally, its main challenges and prospects are considerably pointed out.

Waste Algae for Bioenergy Generation to Mitigate Eutrophication and Greenhouse Emissions in Water Bodies

2023-04-25T10:29:20+00:00

Eutrophication has a significant negative impact on the ecosystem since it depletes the planet's biological resources and is further responsible for climate change. It is caused by both endogenous and exogenous nutrient enrichment. This phenomenon degrades the water quality and simultaneously increases the greenhouse gases emission from waterbodies resulting in climate change Inland waterbodies contain enormous amounts of nutrients such as phosphorous, nitrogen, and carbon. Thus, it becomes essential to restore these nutrients using proper sustainable approaches. Algae-based technologies have received a lot of attention these days because of environmentally friendly and inexpensive treatment. About 70% of the nutrient load from wastewater can be removed using such technology. The recovered algal biomass after wastewater treatment contains various biomolecules which can be used for the producing of value-added products such as bioenergy in the form of biomethane and biodiesel, cosmetics and pharmaceuticals along with the synthesis of nanoparticles. Therefore, the primary goal of this review is to inform readers about the possibilities of a low-cost integrated biorefinery based on microalgae for resource recovery and to mitigate eutrophication and greenhouse gas emission from water bodies.

Byproduct Formation of Chlorination and Chlorine Dioxide Oxidation in Drinking Water Treatment

2023-03-08T07:59:39+00:00

Increasing water scarcity caused by population growth, climate change, pollution from natural and anthropogenic sources, etc. is likely to impact the occurrence of water-associated infectious diseases. Nowadays, access to clean and safe water is a growing concern worldwide. Therefore, disinfection of drinking water is a vital step in public treatment systems as it ensures the removal of various contaminants, including pathogenic microorganisms (protozoa, viruses, bacteria, and intestinal parasites) that give rise to waterborne diseases. Nevertheless, undesirable disinfection byproducts (DBPs) are formed during disinfection as a result of reactions between chemical disinfectants and natural organic matter (NOM), and/or anthropogenic contaminants, and/or bromide/iodide that are present in the raw water. The chemical complexity and heterogeneity of matters in the raw water makes the characterization and the mechanism of DBPs formation quite difficult and ambiguous regardless of the previous hundreds of studies on DBPs generation. As chlorination is still the most economic and most often used disinfection method, and beside chlorination, the application of chlorine dioxide is becoming more widespread, this paper investigates the possible DBPs generated using chlorine and chlorine dioxide with highlighting their adverse health effects. It overviews the reactions of those disinfectants with inorganic and organic compounds. It is important to note that in order to better understand the performance of disinfectants in water treatment, further investigations on the mechanisms of them with inorganic and organic compounds found in water are critically needed.

Usage of the New Modifier-curing Agent in Plywood Technology: The Influence to Urea-formaldehyde Resin Curing and Formaldehyde Emission

2023-01-05T10:48:41+00:00

One of the urgent scientific and technical objectives in the technologies of plywood and wood boards is the search for ways to reduce of hot pressing time without increasing the formaldehyde emission from finished products. To solve this problem was developed the new modifier-curing agent MC-4SF, is mainly a product of interaction of citric acid with urea and ammonia. Compared to traditional ammonium salts, the modifier-curing agent combines the properties of both direct and latent catalysts. Determination of the composition of residual methylol groups in the aqueous extracts obtained by treating the resin cured at 100 °C showed that the modifier-curing agent provides relatively high hydrolytic stability of the UF-polymer during extraction. Spectra of solid-state ¹³C NMR showed that in resins cured with MC-4SF increased the compound of methylene bridges compared to resins cured with standard catalysts. It is possible that the amino groups of urea (or its derivatives) included in the modifier-curing agent, react with the methylol groups of UF oligomers, fitting urea into the structure of the resulting polymer. Thus explains the increased hydrolytic stability and reduced toxicity of the cured resin. Manufacturing tests of nine-layer plywood made with a modifier-curing agent showed that replacing ammonium sulfate with MC-4SF allows a significant reduction in pressing time at 110 °C without loss of quality of the finished product. With the same pressing time, it was possible to increase the line shear strength by 14% and to reduce formaldehyde emission by 45%.

Study on Corrosion Characteristics of Aluminum Alloy Al3102 in Sulfate-reducing Bacteria Environment and Investigating the Use of Azadirachta indica Leaves Extract in its Control

2023-06-01T13:49:43+00:00

An effort to understand the corrosion characteristics of aluminium Al3102 alloy in a neutral medium in the presence of Desulfovibrio desulfuricans was made. The corrosion rate increased up to tenfold in the bacterial medium in comparison to the control (abiotic) medium. Scanning electron microscopy (SEM) studies showed substantial sulfate-reducing bacteria (SRB) adhesion on the alloy surface and pit formation. Supplementation of 1000 ppm Azadirachta indica leaves extract decreased corrosion by 82%. Sulfide analysis, SEM, and X-ray photoelectron spectroscopy (XPS) studies showed a significant effect of neem leaf extract (NLE) on bacterial metabolic activity and confirmed the adsorption of the inhibitor molecules on Al3102 surface. Electrochemical impedance spectroscopy studies showed that the NLE formed a highly resistive external layer which protected the alloy surface from the corrosive effects. The gas chromatography-mass spectroscopy studies (GC-MS) showed appreciable amount of esters, terpenoids, heterocyclic nitrogen, sulfur compounds, and organic bromine compounds in NLE.

Kinetics, Equilibrium and Thermodynamic Studies on Removal of Oleic Acid from Sunflower Oil onto Amberlyst A21

2023-02-16T11:44:12+00:00

Amberlyst A21 was used for the oleic acid adsorption from sunflower oil (SFO). The impacts of parameters such as contact time, temperature, and mass ratio of adsorbent on oleic acid adsorption were studied. The characterization of Amberlyst A21 before and after adsorption was performed by using Fourier transform infrared spectrometer (FTIR) and scanning electron microscope (SEM). The adsorption reached equilibrium 480 minutes later. The increase in temperature and the amount of adsorbent caused an increase in the amount of adsorbed oleic acid. The adsorption kinetics, isotherms, and thermodynamics were studied. The pseudo-first order kinetics well described the adsorption for all studied temperatures. The Langmuir, Freundlich, and Dubinin−Radushkevich isotherms and thermodynamic analysis were investigated at equilibrium. The suitability of the Langmuir and Freundlich isotherms indicated that the adsorption takes place under monolayer and heterogeneous surfaces. Thermodynamical results showed that adsorption occurs spontaneously and endothermic.

Torrefaction: Process Parameters and Reactor Design

2023-03-13T11:06:38+00:00

Torrefaction is a thermochemical process, where biomass is obtained in temperature range from from 200 to 300 °C, in inert atmosphere with the aim to increase carbon content of biomass. In this paper, emphasis is on biomass feedstock types, different effects on torrefaction success, and torrefaction reactors.

Comparison of 624-type Capillary Columns

2023-04-13T12:28:46+00:00

In our research, seven 624-type capillary columns were investigated. All the columns were the same in length, internal diameter, and film thickness (30 m × 0.32 mm × 1.0 µm). However, they were produced by different manufacturers or the same manufacturer but in different batches. Even though the manufacturers recommend them as "equivalent columns" this equivalence did not prevail even in the case of columns produced by the same manufacturer. Our examination criteria centered on the quantitative determination ability of the columns. A homemade column test mixture was compiled to represent all the second-order interactions that can occur between the analyte and stationary phase. Although theoretically these columns have the same stationary phase quality, they did not result in the same chromatograms. In addition to the origin and batch of the column, the "history of the column" contributes likewise to the different peak symmetry, retention order, and even peak areas that affect the quantitative determination. We quantified this quantitative determination ability with the effective carbon number (ECN) and the Limit of Quantitation (LoQ) values. Based on our results the attainable LoQ and ECN values depend at least as much on the origin and actual state of the stationary phase as on the measurement conditions to be optimized. In our paper, we demonstrate the extent to which the same stationary phases offered by different companies and/or different backgrounds can influence our detection limit and detector response even if the relevant columns have theoretically the same chemical structure.

The Effective Carbon Number of Chlorobenzenes

2023-04-04T16:19:23+00:00

Detector response of 12 chlorobenzenes was investigated (mono-, di-, tri-, tetra-, penta-, and hexachlorobenzene, CBs) using flame ionization detector in a capillary gas chromatographic system. We determined the signal-reducing effect of the chlorine atom on the aromatic ring relative to the number of the chlorine substituents and expressed with the effective carbon number (ECN). Benzene was applied as a reference substance. Using the signal-modifying pattern of the chlorine atoms on the benzene's response, we developed an alternative calibration measurement method (CBs-ECN method) for the 12 CBs and compared it with classic calibration. The differences in the concentrations calculated by the two quantitative methods were under 4.5% for 11 CBs and 7% for one compound.
Taking advantage of the opportunities provided by the CBs-ECN pattern it is not necessary to apply all of the 12 CBs but only one single component, the hexachlorobenzene for the calibration. With this simplification, the preparation of the calibration standards is faster, does not require purchasing all 12 CBs for each subsequent calibration, and the exposure to harm and expenses are reduced.

Photometric Determination of Trace Amounts of Aluminum in Nearly Saturated Rock Salt Solutions Used by Chlor-alkali Industry

2023-04-17T10:25:30+00:00

The previously widespread mercury cell technology in chlorine production has now been replaced by more environmentally friendly membrane cell electrolysis which is a Best Available Techniques (BAT) technology. However, this requires a much cleaner brine containing contaminants (Al, Ca, Mg, etc.) in the order of ng/g at most. For this reason, it’s very important to detect trace amounts of aluminum in concentrated saline media in the simplest and fastest way. To the best of our knowledge, no one has previously developed a spectrophotometric method capable of detecting aluminum in ionic forms selectively in the order of ng/g in concentrated saline media, without any preconcentration or separation step. Our advanced analytical method provides an opportunity for this. During the analytical procedure, a colored complex ion is formed from the dissolved aluminum content of the sample with eriochrome cyanine R (ECR) ligand in buffered pH medium. The sensitivity of the measurement is increased by adding quaternary ammonium salt. The colored complex ion is formed in 15 minutes, then the absorbance measurement can be performed for 90 minutes. The effect of rock salt interference was eliminated by proper calibration. In our work the dependence of the signal on temperature, pH, time elapsed after the addition of reactants, the dosing sequence, the salinity of the medium was examined, furthermore, we studied which wavelength-absorbance values give the best fit (highest R² value) and the highest sensitivity in case of linear calibration. Surprisingly, increasing the salinity significantly improves the sensitivity of the measurement.

Total Dissolved Solids, Phenol, and Barium Removals from Oilfield Produced Water Using Kapok Fibers and Ultrafiltration Membrane

2023-04-25T09:07:30+00:00

Oilfield-produced water treatment using raw Kapok fiber (RKF) and a modified surface of Kapok fiber followed by an ultrafiltration membrane was conducted to reduce total dissolved solids (TDS), phenol, and barium. Variables considered in the experiment were contact times (30, 60, 90 min.), the flow rate of samples (5, 6, and 7 L/min), and trans-membrane pressure of ultrafiltration membrane (0.25, 0.35, and 0.50 bar). Raw Kapok fiber and modified surface Kapok fiber were used to investigate the effect of Kapok fiber on total dissolved solids, phenol, and barium removals from produced water. The results showed that raw KF decreased the TDS, phenol, and barium by 51.81%, 62.63%, and 54.20%, respectively. Treatment of raw Kapok fiber column filtrate using ultrafiltration membranes (UF) showed the removal of TDS, barium, and phenol achieved 73.15%, 42.44%, and 79.45%, respectively, at a flow rate of 5 L/min, TMP of 0.25 bar, and contact time of 90 min. Modifying the Kapok fiber surface using sodium hydroxide solution (5 wt%) and hot water (98.5 °C) reduced the TDS, phenol, and barium to 57.32%, 65.83%, and 79.08%, respectively. Further, at the same operating condition, the modified surface of Kapok fiber followed by UF decreased 94.31% TDS, 84.20% phenol, and 56.23% barium, respectively. The results show that modification of the Kapok fiber surface followed by UF can be used to remove the TDS, phenol, and barium from produced water.

Elucidation on Performance and Structural Properties of Skinned Asymmetric Nanofiltration Membrane Based on Theoretical Models

2023-04-05T09:56:14+00:00

In this study, the performance and structural properties of enhanced skinned asymmetric nanofiltration (NF) membranes were experimentally and theoretically analyzed. Based on Donnan and steric-hindrance transport mechanism, the relationship of performances and key properties of the fabricated nanofiltration membranes were examined. At the optimum concentration of polymer, the skinned nanofiltration membranes achieved high salt rejection up to 85% and high solutes separation efficacy. Moreover, morphological and modeling analysis discovered that, the optimum membranes produced good pore size and fine key properties with 1.20 nm of pore radius, 4.96 µm of ratio of thickness to porosity (∆x/A_k) and −1.56 of surface charge, ζ as well as uniform pore size distributions. The findings from this study proved that the strategic utilization and manipulation of good membranes material is a simple and good attempt to upgrade the membranes capability and usability which lead towards the application in various membrane separation processes.

Proton Exchange Membrane Fuel Cells: Focused on Organic-Inorganic Nanocomposite Membranes

2023-05-02T06:36:32+00:00

The application of organic-inorganic nanocomposite membranes allows for a synergy between the desirable thermal and mechanical properties of inorganic materials with the reactivity, dielectric properties, durability, flexibility, and processability of the polymeric materials. Proton exchange membrane fuel cells (PEMFCs) suffer from some problems including water content management, carbon monoxide poisoning, hydrogen reformate, and fuel crossover through the membrane. Herein, specific solutions have been proposed to the above-mentioned problems using organ-inorganic nanocomposites. These solutions include doping proton conductive inorganic nano-particles in the proton exchange membrane, preparing nanocomposites via the sol-gel method, covalence bond of inorganic compounds with the polymer structure, and acid-based proton exchange nanocomposite membranes. Furthermore, hydrogen production with low carbon monoxide content using the ethanol steam reforming method, as well as the effect of CO in the hydrogen feed of PEMFC are explained and discussed. Finally, desirable conditions for achieving the maximum power density in exchange membrane cells (EMFCs) are discussed.

The Effect of Operating Parameters on Total Cross-membrane Flux in a PVDF Flat Sheet Membrane

2023-04-13T12:32:25+00:00

Membrane distillation (MD) is an emerging thermal membrane technology that involves water vapor driven by a vapor pressure gradient over a hydrophobic membrane. MD faces several challenges, one of which is the flux of water vapor. The total cross-membrane flux in membrane distillation was investigated in this paper using the co-current PVDF flat sheet for direct contact. membrane distillation applications. The goal of this research is to improve total cross-membrane flux. The effect of various operational parameters is studied, including feed inlet temperature (333.15–358.15 K), feed flow rate (1–2.5 kg/s), permeate inlet temperature (288.15–313.15 K), and feed inlet NaCl concentration (0.035 to 0.485 kg/kg). To acquire a good value of total cross-membrane flux, their interactions with the total cross-membrane flux are studied in this work. The obtained results were computed during MATLAB-Simulations under several scenarios adopting the Trial-&-Error approach. This last inputs various parameters' values and thus draws the required curves to be discussed and analyzed. The results indicated that the PVDF flat sheet membranes provide a significantly higher total cross-membrane flux at higher feed input temperatures, producing a 73.2075 kg/(m² h) at a feed inlet temperature of 358.15 K, a permeate inlet temperature of 293.15 K, and a flow rate of 2.5 kg/s, with a feed inlet NaCl concentration of 0.035 kg/kg. Feed inlet temperature significantly affected the total flux through the membrane; however, flow rate, permeate inlet temperature, and feed inlet NaCl concentration had a less significant effect.

Cellulose, Cellulose Benzoate and Cellulose Citrate from Screw Pine (Pandanus tectorius) Leaves as PVDF Filler for Improved Permeability and Anti-fouling Properties

2023-04-26T09:46:11+00:00

Cellulose was isolated from screw pine (Pandanus tectorius) leaves through an alkalization and bleaching process and synthesized into cellulose benzoate and cellulose citrate. Cellulose, cellulose benzoate, and cellulose citrate were introduced to polyvinylidene ﬂuoride (PVDF) matrix as fillers via blending-phase inversion method to improve PVDF membrane permeability and anti-fouling properties. The effect of cellulose, cellulose benzoate, and cellulose citrate fillers on PVDF membrane hydrophilicity, permeability, selectivity, anti-fouling properties, and morphology was investigated. The result demonstrates that the PVDF membrane's hydrophilicity, permeability, and anti-fouling properties were improved by the addition of filler. With the addition of 0.3% of cellulose, cellulose citrate, and cellulose benzoate, water permeability in PVDF was doubled. PVDF membrane rejection of methylene blue increased up to 86, 85 and 82%, respectively, with the addition of 0.3% cellulose, cellulose citrate, and cellulose benzoate. Anti-fouling properties value increased up to 89% in 0.3% cellulose citrate addition. These results indicated that cellulose, cellulose benzoate, and cellulose citrate from screw pine leaves are excellent for PVDF membrane fillers which are comparable with other reported membranes.