Packed Bed Column Research Articles

Study of capture efficiency utilizing passive mixing in heterogeneous microfluidic immunosensors

The role of 3-dimensional (3-D) geometries in facilitating surface reactions in microchannels is the subject of the present work. 3-D microfluidic immunosensor geometries inspired from the design of packed bed columns, utilizing splitting and recombination of flows in improving the transport in flow heterogeneous microfluidic immunosensors, were studied systematically. First, the effect of the passive mixing on the antigen capture was tested experimentally using prostate specific antigen (PSA) and anti-PSA and validated using numerical studies. Subsequently, numerical studies on the effects of geometrical parameters like the height and width of the microchannel, the height and width of the grooves, number of groove sets, the ratio of the heights of the grooves and the microchannel etc., on the antigen capture were conducted. The Sherwood number (Sh) and Peclet number (Pe) were used to explain the mass transfer. Finally, the optimum Peclet number (Pe∼x223C 3400) was found, having a maximum figure of merit ratio for the grooved to the ungrooved microchannels Correlations were also obtained between the average surface concentration and the geometrical parameters. The paper presents novel scientific results which are useful for designing efficient heterogeneous immunosensors.

Batch and Packed Bed Column Study for the Removal of Cr (VI) and Ni (II) Using Agro-Industrial Wastes

The objective of this study was to prepare bio adsorbents from agro-industrial wastes from yam starch (YSR) and plantain (PSR) production for its use in the removal of Cr (VI) and Ni (II) in aqueous solution in batch and continuous packed-bed column systems. Bromatological analysis showed that the biomaterials are rich in cellulose, lignin, hemicellulose, and SEM micrographs that evidence a mesoporous structure characteristic of materials of lignocellulosic origin. FTIR evidenced functional groups such as hydroxyl, carbonyl, and methyl, possibly involved in the uptake of metal ions. EDS and FTIR analysis after adsorption confirmed that the retention of the metals on the surface of the adsorbent materials was successful. Cr (VI) and Ni (II) removal efficiencies above 80% were achieved using YSR and PSR in batch systems at the different conditions evaluated. The optimum conditions for removing Ni (II) on PSR were a bed height of 11.4 cm and a temperature of 33 °C, while for YSR, they were: 43 °C and 9 cm for temperature and bed height respectively. The variable with the most significant influence on the removal of Cr (VI) in a batch system on the two bio adsorbents was temperature. In contrast, the adsorbent dose and temperature are relevant factors for PSR Ni (II) removal. Therefore, the residues from the preparation of yam and plantain starch have high potential for removing heavy metals from wastewater and are presented as an alternative for their final disposal.

Continuous biosorption of acid red 27 azo dye by Eichhornia crassipes leaves in a packed-bed column

In this work, the biosorption behavior of acid red 27 (AR27) dye using Eichhornia crassipes leaves (LECs) in a packed-bed column was investigated by varying relevant operational parameters and assessment of mathematical models. Results showed that the zero-charge point of LECs was 2.37 and that optima pH and volumetric flux of the influent solution for AR27 biosorption were 2.0 and 56.5 hbox {L}/hbox {m}^{2}cdot hbox {h}, respectively. The maximum specific and volumetric biosorption capacities were observed at influent AR27 concentrations and with LEC bed heights ranging between 50 and 400 mg/L and 2 and 8 cm, respectively. It was also found that if LEC bed height was increased and volumetric flux and AR27 concentration of the influent solution decreased, service and saturation time increased. Modeling results revealed that the Thomas, bed depth service time, Yoon–Nelson, dose-response, and logistic models accurately described the dynamic performance of the packed-bed column in terms of pH, AR27 concentration, and volumetric flux of influent AR27 solution, as well as that of LEC bed height. The findings revealed that LECs exhibited remarkable potential for the biosorption of AR27 from aqueous solutions in a packed-bed column and could potentially be useful for the treatment of AR27-laden wastewater.

High-solid enzymatic hydrolysis of sugarcane bagasse and ethanol production in repeated batch process using column reactors

The online version contains supplementary material available at 10.1007/s13205-021-02932-3.

Removal of Cresols From Water by Packed Beds of Cyclodextrin-Based Hydrogels

A cyclodextrin-based polymer was prepared by crosslinking β-cyclodextrin with epichlorohydrin to be assessed as a sorbent material for cresols in packed-bed columns. Both Langmuir and Freundlich isotherms were appropriate to describe the sorption equilibrium in the conditions tested, and the thermodynamic parameters obtained for this process confirmed its exothermic nature with similar enthalpies (between − 6.8 and − 8.3 kJ/mol) for the three isomers. The removal of cresols from water was carried out in nine cycles of sorption–desorption in fixed-column experiments with the cyclodextrin hydrogel, achieving sorption capacities of 6.2, 11.6, and 15.1 mg/g for o-, m-, p-cresol, respectively. These differences in sorption capacities are due to the different chemical structures of cresols, that is, the relative position of the methyl and hydroxyl groups. However, similar sorption rates were observed for each isomer, with a mean value of 0.10 mg-cresol g-CDP–1 min–1 in all cases. The experimental data for the breakthrough and the elution curves have been successfully modeled by two effective two-parameter equations, a dose–response model for the sorption step and a pulse-peak model for the regeneration step. The cyclodextrin polymer matrix has been proven to be an effective a good sorbent material for removing cresols from water, exhibiting remarkable reusability performance and structural stability throughout the successive elution steps carried out with methanol.

Selective production of singlet oxygen from zinc-etching hierarchically porous biochar for sulfamethoxazole degradation

Porous carbons are appealing low-cost and metal-free catalysts in persulfate-based advanced oxidation processes. In this study, a family of porous biochar catalysts (ZnBC) with different porous structures and surface functionalities are synthesized using a chemical activation agent (ZnCl2). The functional biochars are used to activate persulfate for sulfamethoxazole (SMX) degradation. ZnBC-3 with the highest content of ketonic group (CO, 1.25 at%) exhibits the best oxidation efficiency, attaining a rate constant (kobs) of 0.025 min−1. The correlation coefficient of the density of CO to kobs (R2 = 0.992) is much higher than the linearity of the organic adsorption capacity to kobs (R2 = 0.694), implying that CO is the intrinsic active site for persulfate activation. Moreover, the volume of mesopore (R2 = 0.987), and Zeta potential (R2 = 0.976) are also positive factors in PS adsorption and catalysis. In the mechanistic study, we identified that singlet oxygen is the primary reactive oxygen species. It can attack the –NH2 group aligned to the benzene ring to form dimer products which could be adsorbed on the biochar surface to reach complete removal of the SMX. The optimal pH range is 4–6 which will minimize the electrostatic repulsion between ZnBCs and the reactants. The SMX degradation in ZnBC/PS system was immune to inorganic anions but would compete with organic impurities in the real wastewater. Finally, the biochar catalysts are filled in hydrogel beads and packed in a flow-through packed-bed column. The continuous system yields a high removal efficiency of over 86% for 8 h without decline, this work provided a simple biochar-based persulfate catalyst for complete antibiotics removal in salty conditions.

A tool for mass transfer evaluation in packed-bed columns for chemical engineering students

This paper presents a Microsoft Excel tool to calculate liquid-gas mass transfer coefficients in packed towers to support numerical design activities in the courses of Unit Operations for Industrial Process and Sustainable Process Design for the Master’s degree in Chemical Engineering of the University of Naples Federico II (Italy).The Mass Transfer Solver Tool (MT Solver Tool) uses several available models to estimate, separately, the values of liquid and gas mass-transfer coefficients and the wet surface area for 144 random and structured packings of interest for absorption/stripping and distillation processes. In addition, a separate spreadsheet can be used in a user-defined mode, to evaluate the mass transfer coefficients with new packing types or to interpret experimental data when the geometrical and physical characteristics of the packing are known. Eventually, the tool is supplied with a data library, where packing geometry and model fitting parameters can be retrieved.The software is aimed to support students and educators in the Unit Operations for Industrial Process and Sustainable Process Design courses. In particular, this is meant to be an example on how the accuracy of design algorithms adopted in unit operation processes is affected by the use of the underpinning correlations for mass transfer rate or pressure drops. Besides, this is aimed to encourage comparison of different correlations when exact field data are not available. Besides, chemical engineers and researchers interested in packed columns design and modelling data may also benefit from the utilization of the software. The MT Solver Tool was introduced to students in a dedicated tutorial lesson after lecturers on packed column design algorithms for distillation, absorption and stripping. Most of the students of the course participated to a group training aimed to simulate the design of an absorption column supported by the MT Solver Tool providing feedback on its application.After the training, an anonymous survey was proposed to the students to monitor the approval rating of the proposed activity and the use of the MT Solver Tool software to support numerical calculations.

A Review on Gas-Liquid Mass Transfer Coefficients in Packed-Bed Columns

This review provides a thorough analysis of the most famous mass transfer models for random and structured packed-bed columns used in absorption/stripping and distillation processes, providing a detailed description of the equations to calculate the mass transfer parameters, i.e., gas-side coefficient per unit surface ky [kmol·m−2·s−1], liquid-side coefficient per unit surface kx [kmol·m−2·s−1], interfacial packing area ae [m2·m−3], which constitute the ingredients to assess the mass transfer rate of packed-bed columns. The models have been reported in the original form provided by the authors together with the geometric and model fitting parameters published in several papers to allow their adaptation to packings different from those covered in the original papers. Although the work is focused on a collection of carefully described and ready-to-use equations, we have tried to underline the criticalities behind these models, which mostly rely on the assessment of fluid-dynamics parameters such as liquid film thickness, liquid hold-up and interfacial area, or the real liquid paths or any mal-distributions flow. To this end, the paper reviewed novel experimental and simulation approaches aimed to better describe the gas-liquid multiphase flow dynamics in packed-bed column, e.g., by using optical technologies (tomography) or CFD simulations. While the results of these studies may not be easily extended to full-scale columns, the improved estimation of the main fluid-dynamic parameters will provide a more accurate modelling correlation of liquid-gas mass transfer phenomena in packed columns.

Intensified phenol and p-cresol biodegradation for wastewater treatment in countercurrent packed-bed column bioreactors

An intensified biodegradation process in packed-bed column bioreactors (PBCB) with microbial cells attached to packing/micro-particles surface was proposed and simulated via a dynamic 3D model with continuity, momentum, and species (comprising biomicro-particles) balance equations in liquid/gas, accumulation of biomicro-particles in packed-bed, diffusion and enzymatic reaction within biofilm and liquid film. Phenol and phenol/p-cresol biological removal by Pseudomonas putida was chosen to discuss the enhanced biodegradation efficiency. The biodegradation in single/dual-substrate systems is significantly upgraded as biomass loading on micro-particles surface increases. Microbial cells addition to the surface of micro-particles is more efficient when the foremost extent of biomass is attached to packing via large biofilms with increased resistance to mass transfer, at low phenol concentrations and liquid velocities. These intensified biodegradation systems aim at maximizing the mass transfer in PBCB for treatment of wastewater having high phenols concentration, without reducing the residence time of liquid or diluting the effluent.

Effective recovery of ytterbium through biosorption using crosslinked sericin-alginate beads: A complete continuous packed-bed column study

The recovery of rare-earth from secondary sources is essential for cleaner production. The development of natural biocomposites is promising for this purpose. Sericin is a waste protein from silk manufacturing. The highly polar groups on the surface of sericin facilitate blending and crosslinking with other polymers to produce biocomposites with improved properties. In this work, we investigate ytterbium recovery onto a natural biocomposite based on sericin/alginate/poly(vinyl alcohol) (SAPVA) in packed-bed column, aiming to establish a profitable application for sericin. Effects of flow rate and ytterbium inlet concentration showed that the highest exhaustion biosorption capacity (128.39 mg/g) and lowest mass transfer zone (4.13 cm) were reached under the operating conditions of 0.03 L/h and 87.95 mg/L. Four reusability cycles were performed under the optimum operating conditions using 0.3 mol/L HNO3. Ytterbium recovery was highly successful; desorption efficiency was higher than 97% and a final ytterbium-rich concentrate (3870 mg/L) was 44 times higher than input concentration. Regenerated beads characterization showed that the cation exchange mechanism plays a major function in continuous biosorption of ytterbium. SAPVA beads also showed higher biosorption/desorption performance for ytterbium than other competing ions. These results suggest the application of SAPVA may be an alternative for large-scale ytterbium recovery.

Residence time distribution study in a pilot-scale liquid phase catalytic exchange (LPCE) column packed with a mixture of hydrophobic and hydrophilic catalysts

Residence time distribution (RTD) measurements were carried out in a packed bed column designed for exchange of hydrogen isotopes. The main objective of the study was to characterize the liquid phase mixing under various processes and operating conditions. The packed bed was composed of a mixture of two different types of catalytic packing materials, i.e., a hydrophobic material and a hydrophilic material. Technitium-99m (99mTc) as sodium pertechnetate was used as a radiotracer for RTD measurements. From the measured RTD curves, mean residence times (MRTs), liquid holdup and degree of mixing of liquid phase were evaluated. An axial dispersion model exchange with stagnant zones was used to simulate the measured RTD curves. The results of model simulation showed that volume fraction of hydrophobic to hydrophilic packing and gas/liquid superficial velocities affect the liquid holdup, bed pressure drop and liquid phase dispersion/mixing characteristics. The results of the present study will help to screen packing, optimize the volume of the packing fractions, design and construct the catalyst and optimize the operating conditions for scale up of the isotope exchange process.

Double-Layer Simulated Moving Bed Chromatography for Ternary Separations: Serialized Layer Configurations

Double-layer simulated moving bed chromatography introduced for the complete ternary separation problems utilizes parallel column configurations. The inlet and outlet streams of paired columns need to be properly split and merged to realize parallel operations with the packed bed columns. To make a pair of split streams, at least one flow control unit is additionally required. Therefore, the double-layer simulated moving bed chromatography that consists of six zones with parallelized two columns required at least 10 pumps to control five internal flow splits and five external inlet and outlet flows. In this work, two alternative layer configurations of the double-layer simulated moving bed were introduced to simplify the internal flow patterns. Applying an orthogonal parameter screening method, the design parameters of the double-layer simulated moving bed processes were optimized. The simplified layer configurations were compared with the standard parallel double-layer configuration in terms of process performances and system pressure decrease.

Process performance improvement for the simultaneous production of ligninolytic enzymes in solid culture using agricultural wastes through the Taguchi method

Despite a large amount of published research on the production of ligninolytic enzymes, the latter are not yet being applied to combat environmental pollution. No cost-effective process has been developed to date. This study describes an improvement of the solid-state fermentation procedure for the production of ligninolytic enzymes via Phanerochaete chrysosporium ATX by applying the Taguchi method and using an agro-industrial waste as substrate. The production of lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac) were simultaneously increased within a packed-bed column. The factors and levels studied were humidity (A: 60, 70, 80%), inoculum concentration (B: 7.5, 10.0, 12.5 × 105 spores/mL), packed density (C: 0.14, 0.16, 0.18 g/mL), and time (D: 6, 8, 10 days). The results showed that humidity was the factor with a higher effect upon LiP and Lac's production, while time was for MnP. Humidity exerted the greatest influence on the global desirability of the process. Improved conditions (A, 60%; B, 1.0 × 106 spores/mL; C, 0.17 g/mL; D, 8 days) were further validated: the results revealed an overall desirability increase of 237% over the unoptimized process. Process performance was likewise maintained at a higher scale (1:10). The results contribute to establishing a cost-effective bioprocess to produce ligninolytic enzymes by reducing the cost associated with raw materials and purification steps.

Optimization of process conditions using RSM and ANFIS for the removal of Remazol Brilliant Orange 3R in a packed bed column

The current investigation explored the potential of biochar produced from Ulva lactuca to continuously adsorb Remazol Brilliant Orange 3R (RBO3R) in a packed bed column. The influencing parameters namely sorbent bed depth, the flowrate of the solute and the initial RBO3R concentration were studied. The process conditions were optimized using the Box Behnken method Response Surface Methodology (RSM) and also the experiment results were predicted using Adaptive Neuro-Fuzzy Interface System (ANFIS). A comparison study was analyzed using statistical error analysis, boxplot and cluster analysis. The experimental results concluded that a correlation coefficient of 0.9981 and 0.9999 was obtained for RSM and ANFIS predictive models. The removal efficiency of 68.6% was obtained at optimum conditions of 15 ​cm sorbent depth, 0.45 ​L/h flowrate and 0.25 ​mmol/L initial RBO3R concentration.

Monitoring Methanol Exposure during Liquor Distillation with a Hand-Held Device

Introduction Toxic methanol occurs naturally in most distillates. Yet, suitable detectors to check product adherence to legal limits and, most importantly, monitor the methanol concentration in situ during distillation are not available. The legal limits for methanol contamination in the E.U. are 1350 g methanol per hL ethanol for Williams pear spirits, 1200 g/hL for apple and plum spirits and 1000 g/hL for cherry spirits. Significantly lower ones apply for brandy (i.e. 200 g/hL), Vodka from agricultural alcohol (30 g/hL) and London gin (5 g/hL). However, these limits are exceeded frequently, as shown for 183 commercial Williams pear spirits with methanol contents up to 1865 g/hL [1]. Usually, distillers rely on error-prone human olfaction while “gold standard” but off-line, time-consuming and expensive liquid or gas chromatography (GC) is rarely used.Here, we monitor methanol concentrations during industrial distillation of cherry, apple, plum and herb liquor (196 samples) with a low-cost and handheld detector. Therein, it quantified individual methanol concentrations (0.1 – 1.25 vol% in liquid) with high coefficient of determination (R2 = 0.92) by headspace analysis, as confirmed by GC. Typical ethanol contents (5 – 90 vol%) and aromas did not interfere, whereas methanol levels above legal limits were recognized within two minutes. As a result, this device enables distillers to guide distillation and check product quality, to prevent deadly methanol exposure and occupational hazard. Method Mash of plum, apple, cherry as well as a mixture of agricultural alcohol and herbs (for herb spirit) were processed in a distillery located in Switzerland (S. Fassbind AG). Distillate samples were drawn every 1 to 10 min (as compatible with the still operation) for sensor and GC analysis. The methanol detector is shown in Figure 1a. In brief, it consists of a needle (Sterican, B. Braun AG) mounted on a 4 mm (inner diameter) Teflon tube, a packed bed column with 150 mg of Tenax TA particles (35 m2/g, Sigma Aldrich), a flame-made chemoresistive gas sensor of 1 mol% Pd-doped SnO2 [2] nanoparticles and a rotary vane pump (135 FZ 3V, Schwarz Precision). The pump and sensor are controlled by a microcontroller (Raspberry Pi Zero W) mounted on a tailor-made printed circuit board with wireless communication to a laptop or smartphone [3].For each measurement, the vial containing the sample is shaken for 30 s, the sampling needle is inserted through the septum and the headspace is extracted at 25 ml/min for 10 s. Thereafter, the sampling needle is removed and ambient air is drawn for 6 min to convey the sample through the separation column and to analyze it by the sensor. Finally, the column and sensor are recovered by flushing with ambient. Methanol is quantified from the sensor response at a retention time of 1.5 - 1.7 min [4], based on previous calibrations in ternary mixtures of 0.1, 0.3, 0.5, 0.70, 1, and 1.25 vol% methanol (> 99.9 %, Sigma Aldrich) in 10, 30, 50, 70, 90 vol% ethanol (> 99.8 %, Fisher Scientific) and water (Milli-Q Synthesis A10, Merck). Results and Conclusions Figure 1b shows the results of selected samples (for better visibility) for plum (triangles), apple (circles), cherry (squares) and herb (stars), Already low methanol concentrations of 0.1 (cherry), 0.13 (apple) and 0.21 vol% (plum) in the mash (first data points) of the fermented fruits are detected. Highest methanol levels occur in plum distillates (triangles) that vary between 1.2 and 0.85 vol% and only drop significantly after 80 min reaching 0.2 vol% at the end of distillation. Similar methanol dynamics were observed for apple (circles), though at slightly lower concentrations ranging from 1 to 0.7 for t < 80 min. Distinctly lower methanol levels (0.5 – 0.4 vol%) were measured for cherry (squares). Lastly, there is herb spirit (stars) where methanol concentrations stayed constantly below 0.22 vol%. So, the handheld detector is able to follow the individual methanol dynamics of fruit and herb during distillation. Figure 1c shows a scatter plot of methanol concentrations in all (196) samples of herb (stars), cherry (squares), apples (circles) and plum (triangles) distillates, as measured by the handheld device and GC. Close agreement (ideal line, dashed) is observed over the entire concentration range of 0.1 to 1.25 vol%, as quantified with high coefficient of determination (R2 = 0.92).As a result, this handheld device is capable to identify critical methanol levels and could support distillers who mostly rely on olfactory analysis that is error-prone (given the indistinct smell of methanol over ethanol). Since the detector is fully integrated, pocket-sized, battery operated, indicating results on a laptop or smartphone and consists mostly of low-cost components, it is ideal for on-site application and should be affordable even for small distilleries.

Compact Formaldehyde Detector Based on Filter–Sensor System with Validated Performance in Indoor Air

Introduction Formaldehyde is a carcinogenic indoor air pollutant emitted from wood-based furniture, building materials, paints and textiles.[1] Yet, no low-cost sensor exists for on-site monitoring to fulfill stringent current and upcoming (e.g., 8 parts-per-billion by volume, ppb, in France by 2023) exposure guidelines. Here, we present an inexpensive and handheld formaldehyde detector with proven performance in real indoor air. Selectivity is achieved by a compact packed bed column of nanoporous polymer sorbent that separates formaldehyde from interferants present in ambient air. Downstream, a highly sensitive nanoparticle-based chemoresistive Pd-doped SnO2 sensor detects formaldehyde in the relevant concentration range down to 5 ppb within 2 min. Method The handheld formaldehyde detector consists of a separation column and a chemoresistive microsensor [2]. The Separation column consists of a packed bed of Tenax TA powder (500 mg poly(2,6-diphenyl-p-phenylene oxide), 60–80 mesh, ~35 m2 g-1, Sigma-Aldrich) packed inside a Teflon tube (4 mm inner diameters) and secured on both ends with silanized glass wool plugs [3]. The sensor is based on a Pd-doped SnO2 nanoparticle film prepared by flame spray pyrolysis (FSP) and directly deposited onto microsensor substrates [4]. The measurement of emissions from wood products was based on standard testing protocol EN-717-1 to ensure comparable results. Measurements with room air were performed by exposing the detector directly to air from the laboratory. To also test higher concentration, room air was spiked with additional formaldehyde from the gas standard on a dynamic gas mixing setup. Results and Conclusions The concept of the formaldehyde detector is illustrated in Figure 1a–c. Indoor air contains >250 different analytes that are separated by a packed bed separation column of commercial Tenax TA particles. Tenax TA offers a high surface area (25 m2 g-1) due to its macroporous structure (Type II adsorption isotherm, Figure 1d) with a volume-average pore size of 120 nm (inset in Figure 1d). This enables efficient adsorption and retention of analytes, similar to a gas chromatographic column, though much more compact (13 cm length), inexpensive (˂ $20 for the Tenax TA powder) and without the need for column heating. After the column, formaldehyde is detected separately from interferants (e.g., hydrogen, methanol), thus selectively, by a highly sensitive but non-specific chemoresistive microsensor (Figure 1e). It consists of a highly porous film of flame-made and directly deposited Pd-doped SnO2 nanoparticles (Figure 1f) that form fine networks with large surface area (54.5 m2 g-1) for formaldehyde detection down to 5 ppb..We validated this detector on real indoor air samples from our laboratory (Figure 2a). First, it shows a large response from non-retained compounds that might be CH4, CO and H2. These gases are all usually present at hundreds of ppb in indoor air. Thereafter, a smaller peak is detected (SNR >40, see inset) at 107 s corresponding to formaldehyde at 45 ppb according to a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS). It is not interfered by methanol and ethanol, which are both eluted later, in line with synthetic gas mixtures. Figure 2b shows the scatter plot of the formaldehyde concentration measured by the detector and PTR-TOF-MS for pristine (squares, measured on two different days) and formaldehyde-spiked indoor air (circles) in the range of 14–475 ppb. Both instruments show excellent agreement with an R2 of 0.996, despite the challenging lab environment with high and varying background concentrations of acetone (up to 1,000 ppb) and ethanol (up to 4,000 ppb). Most importantly, the detector shows a low average error of only 10 ppb and can clearly differentiate safe levels from such above the WHO guideline (dashed line) and when immediate sensory irritation (dotted line) occurs.As a result, based on its compact size and low price, this device is promising for monitoring of formaldehyde in indoor air. When interconnected, such next-generation low-cost detectors could enable distributed chemical recognition (Figure 2c) for air quality in “smart” buildings and “future” cities [5].

Solid-State Cultivation of Aspergillus niger-Trichoderma reesei from Sugarcane Bagasse with Vinasse in Bench Packed-Bed Column Bioreactor.

Solid-state cultivation (SSC) is microbial growth on solid supports under limited water conditions. Citric acid is a microbial aerobic metabolic product with several industrial applications, with production potential that can be obtained by SSF. Several wastes from agro-industries are used in SSF, such as sugarcane bagasse and vinasse. Cultures of mixed fungi or co-cultures are used in this SSF in order to complement the inoculum's xylanolytic enzymes for action on the lignocellulosic material (bagasse). Thus, this study aims to evaluate the effect of inoculum (Aspergillus niger and Trichoderma reesei consortium) in the production of citric acid from sugarcane bagasse impregnated with vinasse using bench packed-bed reactors (PBR). The results show the importance of T. reesei and A. niger in inoculum at a ratio of 50:50 and 25:75, suggesting the use of solid support due to the complementation of the hydrolytic enzymes. The highest concentration of citric acid, approximately 1000mgL-1, was obtained for 100mm of bed height in 48 and 72h, with maximum glucose yield in citric acid (2.2mg citric acid mg glucose-1). kLa indicates that maintaining solid moisture and liquid film thickness is important to keep the oxygen transfer in SSC.

Water from Air: Desiccant System Design and Simulation

Air water generators that harvest water from air humidity have the potential to counter the ever-rising problem of drinking water scarcity. There are many different types of air water generation systems that work on various different principles. Desiccant based air water generation systems work on the principle of moisture absorption, consisting of a packed bed dehumidifier that absorbs the moisture from air. This reduces the energy requirement of the system. To discuss the efficiency of the system, it is crucial to understand the working of the packed bed column. In this paper, a mathematical model has been developed for a packed bed dehumidification system using aqueous CaCl2 as the liquid desiccant. This model has been developed using water saturation pressure and equilibrium relative humidity models. The packed bed model has been used to study the effect of various input parameters like air and desiccant flow rate, packing material, relative humidity and desiccant concentration, on the capacity of the desiccant to absorb water from air. The results so obtained can be used to predict the water that can be absorbed by the desiccant in the packed bed column for given inlet conditions.

Fixed bed biosorption and ionic exchange of aluminum by brown algae residual biomass

This study aimed to evaluate the ion exchange and biosorption of Al3+ using as biosorbent material residual biomass generated in the alginate extraction process from the brown algae S. filipendula (named RES). The batch mode results showed that ion exchange, mainly with Na+ ions, has important participation in the removal of Al3+ ions by RES. Characterization analyses and blocking assays indicated that carboxylic, amino and sulfonate functional groups play a key role on the Al3+ biosorption. The dynamic system in a fixed packed bed column and the reuse/regeneration of the biosorbent was assessed by breakthrough method. Fixed bed experiments pointed that higher Al3+ removal was achieved at 0.5 mL/min and 1 mmol/L. DualSD model showed superior prediction of experimental data. Biosorption/Desorption cycles demonstrated the reuse feasibility of the biosorbent, which maintained a considerable adsorption capacity in all cycles performed.

Kinetics and equilibrium adsorption of phosphate on lanthanum oxide supported on activated carbon

Understanding the thermodynamics and kinetics of phosphate adsorption is crucial in the design of packed-bed columns for phosphate removal, particularly in clinical applications such as dialysis, in which limited contact time is available. Studies have shown that the kinetics of phosphate adsorption on metal oxides is a two-step process: rapid initial adsorption that occurs in a few minutes to a few hours is followed by slower adsorption that may last for days. In this work, the thermodynamics and kinetics of phosphate adsorption on lanthanum oxide impregnated on activated carbon (La-AC) are investigated to explain its phosphate adsorption behavior. The phosphate adsorption mechanism was investigated by studying (1) the effects of temperature on phosphate adsorption capacity, (2) the dynamics and enthalpy of adsorption using flow microcalorimetry (FMC), (3) the kinetics of phosphate adsorption, and (4) the relationship between the amount of phosphate adsorbed and the amount of hydroxide released. Phosphate adsorption on La-AC followed the Langmuir isotherm. FMC results indicate that phosphate adsorbed through several mechanisms, principally through the formation of monodentate and bidentate inner-sphere surface complexes. A pseudo-second-order kinetic model is typically used to model phosphate adsorption; however, it was found that a kinetic model developed based on the assumption of two parallel surface adsorption reactions fits the measured adsorption kinetics significantly better than the pseudo-second order kinetic model that is almost universally used to describe phosphate adsorption kinetics. • Lanthanum-impregnated activated carbon was investigated as a phosphate adsorbent. • Phosphate adsorption was well described by the Langmuir isotherm. • Phosphate anions adsorbed on lanthanum surface via a parallel path mechanism. • A kinetic model based on the parallel path mechanism was developed. • Parallel path model fit kinetics much better than the pseudo-2nd-order model.