scholarly journals Biocatalytic Reduction of Formaldehyde to Methanol: Effect of pH on Enzyme Immobilization and Reactive Membrane Performance

2021 ◽  
Vol 16 (3) ◽  
pp. 472-480
Author(s):  
Norhayati Abdul Rahman ◽  
Fauziah Marpani ◽  
Nur Hidayati Othman ◽  
Nur Hashimah Alias ◽  
Junaidah Jai ◽  
...  
Keyword(s):  
Enzyme Immobilization ◽  
Enzymatic Reaction ◽  
Feed Solution ◽  
Permeate Flux ◽  
High Concentration ◽  
Enzyme Loading ◽  
Reaction Conversion ◽  
Observed Rejection ◽  
Pes Membrane ◽  
Reactive Membrane

Thermodynamic stabled CO2 molecules can be biocatalytically reduced to methanol via three cascade dehydrogenases (formate, formaldehyde and alcohol) with the aid of cofactor as the electron donor. In this study, Alcohol dehydrogenase (EC 1.1.1.1), the third step of the cascade enzymatic reaction which catalyzed formaldehyde (CHOH) to methanol (CH3OH) will be immobilized in an ultrafiltration membrane. The enzyme will be immobilized in the support layer of a poly(ether)sulfone (PES) membrane via a technique called fouling induced enzyme immobilization. The objective of this study is to evaluate the effect of varying pH (acid (pH 5), neutral (pH 7) and alkaline (pH 9)) of the feed solution during immobilization process of ADH in the membrane in terms of permeate flux, observed rejection, enzyme loading and fouling mechanism. The experiment was conducted in a pressure driven, dead-end stirred filtration cell. Reaction conversion and biocatalytic productivity will be also evaluated. The results showed that permeate flux for acid solution were the lowest during immobilization. High concentration polarization and fouling resistance cause lower observed rejection for pH 7 and 9. Enzyme loading for pH 5 give 73.8% loading rate which is the highest compared to 62.4% at pH 7 and 70.1% at pH 9. Meanwhile, the conversion rate during the reaction shows that reaction on fouled membrane showed more than 90% conversion for pH 5 and 7. The fouling model predicted that irreversible fouling occurs during enzyme immobilization at pH 7 with standard blocking mechanism while reversible fouling occurs at pH 5 and 9 with intermediate and complete blocking, respectively. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

scholarly journals Effect of pH on membrane fouling during alcohol dehydrogenase immobilization in PES membrane

2020 ◽  
Vol 3 (2) ◽  
pp. 30
Author(s):  
Nurshahira Hazwani Hamran ◽  
Fauziah Marpani ◽  
Nur Hidayati Othman ◽  
Nik Raikhan Nik Him ◽  
Nur Hashimah Alias ◽  
...  
Keyword(s):  
Alcohol Dehydrogenase ◽  
Enzyme Immobilization ◽  
Membrane Fouling ◽  
Feed Solution ◽  
Permeate Flux ◽  
Enzyme Loading ◽  
Solution Ph ◽  
Observed Rejection ◽  
Pes Membrane ◽  
Blocking Mechanism

Fouling-induced enzyme immobilization is a technique to immobilize enzyme by positively manipulating the knowledge of membrane fouling. In this study, Alcohol dehydrogenase (ADH) (EC 1.1.1.1) was immobilized in the support layer of ultrafiltration PES membrane at different solution pH (acid, neutral and alkaline). ADH catalyses formaldehyde (CHOH) to methanol (CH3OH) and simultaneously oxidised nicotinamide adenine dinucleotide (NADH) to NAD+. The initial feed amount of enzyme is 3.0 mg. The objective of the study aims at the effect of different pH of feed solution during enzyme immobilization, in terms of permeate flux, observed rejection, enzyme loading and fouling mechanism. The results showed that, pH 5 holds the highest enzyme loading which is 65% while pH 7 holds the lowest at 52% out of 3.0 mg as the initial enzyme feed. The permeate flux for each pH decreased with increasing cumulative permeate volume. The observed rejection is inversely correlated with the pH where increase in pH will cause a lower observed rejection. The fouling model predicted that irreversible fouling occurs during enzyme immobilization at pH 7 with standard blocking mechanism while reversible fouling occurs at pH 5 and 9 with intermediate and complete blocking, respectively.

scholarly journals Organic Fouling Impact in a Direct Contact Membrane Distillation System Treating Wastewater: Experimental Observations and Modeling Approach

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 493
Author(s):  
Amine Charfi ◽  
Fida Tibi ◽  
Jeonghwan Kim ◽  
Jin Hur ◽  
Jinwoo Cho
Keyword(s):  
Particle Size ◽  
Membrane Fouling ◽  
Direct Contact ◽  
Feed Solution ◽  
Membrane Distillation ◽  
Mixed Solution ◽  
Permeate Flux ◽  
Direct Contact Membrane Distillation ◽  
Organic Fouling ◽  
Specific Cake Resistance

This study aims to investigate the effect of operational conditions on organic fouling occurring in a direct contact membrane distillation (DCMD) system used to treat wastewater. A mixed solution of sodium alginate (SA) and bovine serum albumin (BSA) was used as a feed solution to simulate polysaccharides and proteins, respectively, assumed as the main organic foulants. The permeate flux was observed at two feed temperatures 35 and 50 °C, as well as three feed solution pH 4, 6, and 8. Higher permeate flux was observed for higher feed temperature, which allows higher vapor pressure. At higher pH, a smaller particle size was detected with lower permeate flux. A mathematical model based on mass balance was developed to simulate permeate flux with time by assuming (i) the cake formation controlled by attachment and detachment of foulant materials and (ii) the increase in specific cake resistance, the function of the cake porosity, as the main mechanisms controlling membrane fouling to investigate the fouling mechanism responsible of permeate flux decline. The model fitted well with the experimental data with R2 superior to 0.9. High specific cake resistance fostered by small particle size would be responsible for the low permeate flux observed at pH 8.

scholarly journals Treatment of Synthetic Produced Water using Hybrid Membrane Processes

2018 ◽  
Vol 22 (2) ◽  
Author(s):  
N. Chin ◽  
S. O. Lai ◽  
K. C. Chong ◽  
S. S. Lee ◽  
C. H. Koo ◽  
...  
Keyword(s):  
Tio2 Nanoparticles ◽  
Produced Water ◽  
Removal Rate ◽  
Pure Water ◽  
Water Flux ◽  
Transmembrane Pressure ◽  
Oil Removal ◽  
Permeate Flux ◽  
Uf Membranes ◽  
Pes Membrane

The study was concerned with the treatment of tank dewatering produced water using hybrid microfiltration (MF) and ultrafiltration (UF) processes. The pre-treatment MF membrane was fabricated with polyethersulfone (PES), n-methyl-2-pyrrolidone (NMP) and polyvinylpyrrolidone (PVP). The UF membranes meanwhile contained additional component, i.e., titanium dioxide (TiO2) nanoparticles in the range of zero to 1.0 wt.%. The membrane performances were analysed with respect to permeate flux, oil removal and flux recovery ratio. An increase in TiO2 nanoparticles enhanced the pore formation, porosity and pure water permeability due to improved hydrophilicity. The permeate flux of UF membranes increased with the increase of TiO2 nanoparticles and pressure. The oil removal rate by MF process was only 52.35%, whereas the oil rejection efficiency was between 82.34% and 95.71% for UF process. It should be highlighted that the overall oil removal rate could achieve as high as 97.96%. Based on the results, the PES membrane incorporated with 1.0 wt.% TiO2 was proved to be the most promising membrane at a transmembrane pressure of 3 bar. Although 1.0 M NaOH solution could be used as cleaning agent to recover membrane water flux, it is not capable of achieving good results as only 52.18% recovery rate was obtained.

scholarly journals Pre-fermentative treatment of a model wine with aim to serve as a functional food with decreased alcohol content

2017 ◽  
Vol 63 (01) ◽  
pp. 47-53
Author(s):  
Irina Mladenoska ◽  
Verica Petkova ◽  
Tatjana Kadifkova Panovska
Keyword(s):  
Enzyme Activity ◽  
Gluconic Acid ◽  
Functional Food ◽  
Ph Value ◽  
Enzymatic Reaction ◽  
Alginate Beads ◽  
High Concentration ◽  
Ph Optimum ◽  
Enzyme Preparations ◽  
Initial Ph

The effect of substrate concentration on the enzyme activity in the reaction of glucose conversion into gluconic acid was investigated by using three different enzyme preparations in media with two different glucose concentrations. The media were simulating the conditions in the must, thus named as minimal model must, and were composed form combination of several organic acids and glucose. Those media were having initial pH of 3.5 that is a very unfavorable for glucose oxidase activity having a pH optimum at the pH value of 5.5. Among the three preparations used, the bakery additive, Alphamalt Gloxy 5080, was the most active in the medium with glucose concentration of 10 g/L, showing conversion of more than 70% for the period of 24 h, while the same enzyme preparation in the medium with 100 g/L glucose converted only about 7% of glucose. The pH value of the medium at the beginning and at the end of the enzymatic reaction was a good indicator of the enzyme activity. It seems that for the conversion of glucose in higher concentration, enzymatic preparation in high concentration should also be used. The preliminary attempt of immobilization of two preparations of glucose oxidases in alginate beads was also performed and a successful immobilization procedure for utilization in food industry was preliminarily developed. Keywords: glucose oxidases, enzymatic pretreatment, glucose, gluconic acid, model wine, functional food

scholarly journals Fabrication and Performance Evaluation of Integrated Solar-Driven Membrane Distillation System with Serpentine-shape of Flat Plate Solar Collector for Seawater Desalination

2019 ◽  
Vol 23 (3) ◽  
Author(s):  
M. A. H. M. Hanoin ◽  
N. S. Mohammed ◽  
M. A. I. Z. Arris ◽  
A. I. A. Bakar ◽  
N. M. Mokhtar ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Flat Plate ◽  
Solar Collector ◽  
Pure Water ◽  
Feed Solution ◽  
Membrane Distillation ◽  
The Self ◽  
Permeate Flux ◽  
Salt Rejection ◽  
Flat Plate Solar Collector

Solar-powered membrane distillation (SPMD) system has gained its popularity in desalination application for past decade credit to the system efficiency in producing pure water and the utilization of renewable energy. However, most of the past SPMD works used commercial solar thermal collector (STC) as the thermal energy supply to the feed solution and the study only focused on the performance of the system in terms of flux and salt rejection. In this work, a self-made flat plate solar collector (FPSC) with the serpentine-shape pipe was designed and fabricated to study the effect of the STC towards the membrane performance. Before testing, a simulation work of the fluid flow inside the serpentine-shape pipe of the FPSC was analyzed using NX 10.0 computer-aided design simulation. After that, the efficiency of the self-made FPSC system was tested directly to sunlight in order to identify the maximum irradiance and the temperature of the feed solution. Due to the fluctuation of solar irradiance, the experimental setup of the SPMD system was tested using a solar simulator, and the performance was compared with the membrane distillation (MD) system without integration with FPSC system. Based on the simulation data, it can be concluded that the heat losses across the pipe are due to the slower fluid velocity and sudden pressure drop, which attributed to centripetal force and pressure differences. Meanwhile, the outdoor evaluation data showed that the temperatures of collector and water inside the feed tank could reach up to 84°C and 64°C, respectively when the maximum irradiance of 938 W/m2 was applied. For the performance evaluation between with and without the self-made FPSC system, it can be seen that only marginal difference can be observed for the permeate flux and salt rejection with an average difference of 6.06% and 1.29%, respectively.

scholarly journals Experimental and Theoretical Analysis of Lead Pb2+ and Cd2+ Retention from a Single Salt Using a Hollow Fiber PES Membrane

Membranes ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 136
Author(s):  
Salwa Hadi ◽  
Ahmed A. Mohammed ◽  
Sama M. Al-Jubouri ◽  
Mahmood F. Abd ◽  
Hasan Shaker Majdi ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Metal Concentration ◽  
Peclet Number ◽  
Film Theory ◽  
Heavy Metal Concentration ◽  
Feed Solution ◽  
Membrane Thickness ◽  
Permeation Flux ◽  
Péclet Number ◽  
Pes Membrane

The present work reports the performance of three types of polyethersulfone (PES) membrane in the removal of highly polluting and toxic lead Pb2+ and cadmium Cd2+ ions from a single salt. This study investigated the effect of operating variables, including pH, types of PES membrane, and feed concentration, on the separation process. The transport parameters and mass transfer coefficient (k) of the membranes were estimated using the combined film theory-solution-diffusion (CFSD), combined film theory-Spiegler-Kedem (CFSK), and combined film theory-finely-porous (CFFP) membrane transport models. Various parameters were used to estimate the enrichment factors, concentration polarization modulus, and Péclet number. The pH values significantly affected the permeation flux of the Pb2+ solution but only had a slight effect on the Cd2+ solution. However, Cd2+ rejection was highly improved by increasing the pH value. The rejection of the PES membranes increased greatly as the heavy metal concentration rose, while the heavy metal concentration moderately affected the permeation flux. The maximum rejection of Pb2+ in a single-salt solution was 99%, 97.5%, and 98% for a feed solution containing 10 mg Pb/L at pH 6, 6.2, and 5.7, for PES1, PES2, and PES3, respectively. The maximum rejection of Cd2+ in single-salt solutions was 78%, 50.2%, and 44% for a feed solution containing 10 mg Cd/L at pH 6.5, 6.2, and 6.5, for PES1, PES2, and PES3, respectively. The analysis of the experimental data using the CFSD, CFSK, and CFFP models showed a good agreement between the theoretical and experimental results. The effective membrane thickness and active skin layer thickness were evaluated using the CFFP model, indicating that the Péclet number is important for determining the mechanism of separation by diffusion.

Effect of the operating parameters on the separation of metal chelates using low pressure reverse osmosis membrane (LPROM)

2000 ◽  
Vol 41 (10-11) ◽  
pp. 135-142 ◽  
Author(s):  
Z. Ujang ◽  
G.K. Anderson
Keyword(s):  
Factorial Design ◽  
Metal Removal ◽  
Feed Solution ◽  
Metal Chelates ◽  
Operating Conditions ◽  
Operating Parameters ◽  
Operating Pressure ◽  
Permeate Flux ◽  
Experimental Conditions ◽  
Central Composite

This paper describes an investigation on the effect of operating parameters on the separation of metal chelates using LPROM. The objective of this study was to optimise the process of metal chelates removal by a LPROM using statistical factorial design. Factorial experiment by statistical design was applied, in which a central composite factorial design (half replicate) was used, then followed up by a star design to give a central composite factorial design. A bench-scale spiral wound configuration of sulphonated polysulphone LPROM was used at various operating conditions, i.e. operating conditions, solute concentrations, EDTA, pH and temperature. It has been shown experimentally that the effect of pressure is non-linear with respect to percentage of metal removal at different concentrations of metal ions in the feed solution. Observation of the response surface implies that the operating pressure was not the significant parameter in determining the percentage of zinc removal in the LPROM. The operating pressure, temperature and concentration of EDTA in the feed solution were the most significant parameters for permeate flux variation. It can also be concluded that for a given set of feed and experimental conditions, permeate flux increased linearly with operating pressure and temperature. The other parameters, i.e. the concentration of zinc in the feed solution and pH, were not statistically significant.

High-Concentration Graphene Dispersions with Minimal Stabilizer: A Scaffold for Enzyme Immobilization for Glucose Oxidation

2014 ◽  
Vol 20 (19) ◽  
pp. 5752-5761 ◽  
Author(s):  
Zhenyu Sun ◽  
Jeevanthi Vivekananthan ◽  
Dmitrii A. Guschin ◽  
Xing Huang ◽  
Volodymyr Kuznetsov ◽  
...  
Keyword(s):  
Enzyme Immobilization ◽  
Glucose Oxidation ◽  
High Concentration

Deliberate Salinization of Seawater for Desalination of Seawater

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Francisco J. Arias
Keyword(s):  
Volume Fraction ◽  
Feed Solution ◽  
Economic Feasibility ◽  
Seawater Desalination ◽  
High Concentration ◽  
Electrical Grid ◽  
Draw Solution ◽  
Cost Of Energy ◽  
Salt Deposits ◽  
The Cost

The basis of a novel method for seawater desalination is outlined. In this work, pressure-retarded osmosis (PRO) energy is obtained and used posteriorly for the reverse osmosis (RO) process for seawater desalination. Although PRO process coupled with an RO process has been studied in the past, however, in this work, there is a fundamental difference. Instead of bringing river or wastewaters with low salinity to the coast to be mixed with the seawater to run the PRO process, here is the seawater which is deliberately salinized. This technique has one important consequence, namely, that it is no longer required to be in places where rivers or wastewaters flow into the sea. This important difference eliminates this until now somehow paradoxical requirement if one considers that regions needing desalination are generally poor of water resources. On the other hand, it is not a coincidence that regions needing desalination plants are also regions with rich open salt deposits in the neighborhood; high evaporation, high concentration of salt deposits, and the need for freshwater are all of them directly correlated. Therefore, the idea proposed in the paper is consistent with the problem. The high evaporation in the region which is causing the need for desalination also is creating the solution to do this by using the salt deposits created. The economic feasibility of this method is preliminarily assessed in terms of the thermodynamic limits of extractable energy and then with the cost of the salt required to obtain this energy which is compared with the price from electrical grid. It was found that in order to reduce the amount of salt required for the process, and to make the cost of energy competitive, it is necessary to direct the hypersaline draw solution (draw solution) in a cyclic loop and to have the highest possible volume fraction for the nonsalinized solution (feed solution). Additional R&D is required to explore the possibilities of this concept.

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