Semi-continuous Process Research Articles

Demonstrating scalability between two blender types using DEM

Powder blending is a critical step in pharmaceutical manufacturing that can impact product quality such as tablet tensile strength. This study utilized the Discrete Element Method (DEM) to investigate blending in a 5-liter mini-batch and a 2-liter Turbula blender. DEM parameters were calibrated using small-scale powder characterization tests, so that the particle behavior in the DEM simulations matches the measured behavior. The research explored the effects of blender designs and process conditions on blending and lubricant dispersion. A predictive model for tablet tensile strength was developed. The model takes the lubricant’s dispersion via the lubrication energy into account. The model is then used to predict the tablet tensile strength depending on the chosen process parameters, blending speed, duration, and fill level. DEM simulations enabled scaling between the two blenders, providing valuable insights for a semi-continuous manufacturing process based on mini-batch blending. The findings contribute to a deeper understanding of blending mechanics, offering potential enhancements in pharmaceutical manufacturing efficiency and product consistency.

High efficiency production of 5-hydroxyectoine using metabolically engineered Escherichia coli

The 5-hydroxyectoine is a natural protective agent with long-lasting moisturising and radiation resistance properties. It can be naturally synthesized by some extremophiles using the “bacterial milking” process, but this can corrode bioreactors and downstream purification may cause environmental pollution. In this study, an engineered Escherichia coli (E. coli) strain was constructed for the 5-hydroxyectoine production. First, three ectoine hydroxylases were characterised and the enzyme from Halomonas elongata was the most effective. The L-2,4-diaminobutyrate transaminase mutant was introduced into the engineered strain, which could accumulate 2.8 g/L 5-hydroxyectoine in shake flasks. By activating the glyoxylate cycle and balancing the α-ketoglutarate distribution, the 5-hydroxyectoine titer was further increased to 3.4 g/L. Finally, the optimized strain synthesized 58 g/L 5-hydroxyectoine via a semi-continuous feeding process in a NaCl-free medium. Overall, this study reported the highest titer of 5-hydroxyectoine synthesized by E. coli and established a low-salt fermentation process through the aforementioned efforts.

Mercerisation Followed by Wet on Wet Reactive Dyeing of Cotton Fabric

The commonly employed textile wet processing methods are singeing, de-sizing, scouring, bleaching, mercerising, dying, printing, and finishing. However, these methods are more time-consuming and require a lot of energy, manpower, and chemicals. Therefore, this research aims to develop a semi-continuous processing route that minimizes these problems. In this study, two dying routes were employed. The first is a control group, which was done by conventional mercerisation and dyeing procedures, whereas the second is a semi-continuous experimental group, which has been employed by mercerisation followed by wet-on-wet (WOW) reactive dying. That is, after mercerisation, the fabric, which contains the optimum alkali concentration, goes to dyeing without washing. Washing and titration were performed to determine the optimum alkaline concentration in the fabric at a specific washing cycle. Fabrics that were washed at different cycles after mercerisation were dyed, and their washing fastness, degree of dye exhaustion, fixation, and colour strength were evaluated, and they had a slightly greater colour strength than conventionally dyed fabrics. This is because with a wet-on-wet dyeing procedure, the fabric is relaxed after mercerisation, which allows it to absorb more dye, and the leftover alkali in the fabric is used to fix the dye to the cellulose. The study shows that the optimal washing cycle for passing the optimum alkali concentration is one. Furthermore, the optimal amount of alkali remaining in the fabrics is 3–3.5%. As compared to the conventional dyeing process, this process is economical.

A piece-wise reconstruction of some mechanistic steps in Pickering emulsion polymerization: a semicontinuous styrene montmorillonite-supported process as a case example

AbstractBuilding on traditional emulsion polymerization research, which continues to yield results up to the present day, techniques have emerged to produce hybrid materials. One such technique is Pickering emulsion polymerization, with numerous industrial applications. Despite a growing interest in Pickering emulsion polymerization, the intrinsic mechanisms involved have been based mainly on the findings of classical emulsion polymerization. In this work, by relying on a minimum of assumptions and using a simple model and experimental data on conversion and particle size, we obtain information about the prevailing mechanisms. More specifically, we present four main findings based on data reported previously in the literature. First, in contrast to the three rate-of-reaction intervals reported in classical emulsion polymerization, the integro-differential method yielded only two rate-of-reaction intervals against conversion. Second, a master curve is constructed by plotting the reaction rate against overall conversion, showing a maximum of approximately 55% conversion. Third, despite having a semicontinuous process, monomer concentration inside the particles is not constant. Finally, particle density is a strong function of the Pickering agent concentration, where two fitting parameters (nucleation and coagulation) allowed an accurate description for the particle number time evolution. Both parameters showed a power-law dependence with clay concentration.

Acclimation dynamics of Chlorella vulgaris to sudden light change

Chlorella vulgaris photoacclimation was monitored over eight instantaneous light intensity changes. The intensities ranged between 35μmol PhotonPAR.m−2.s−1 and 600μmolPhotonPAR.m−2.s−1. Cultures were grown in ultra-thin flat panel photobioreactors under continuous light and maintained in low cell density to ensure homogeneous light availability. Photoacclimation was evaluated through spectral quantification of pigments and fluorometric assays. The former gave access to a proxy of chlorophyll and carotenoid content, the latter to the Photosystem-II cross-section (σPSII) and qualification of the photosynthetic machinery (viaOJIP assays). Both the acclimated steady-state values of pigment content and the dynamic of their evolutions after sudden light intensity change were monitored. The characteristic times of the transitions were estimated based on a first-order assumption. Results consistently showed that antenna size adjustment of Chlorella vulgaris was primarily dictated by the light availability, both regarding the acclimated steady-state values and the acclimation dynamics. An energetic limitation was highlighted by the acclimation dynamics at low light. The characteristic time of transition was estimated to be 16.6±2.17h for the transition to the lowest light intensity (35μmol PhotonPAR.m−2.s−1) and 3.55±1.01h for intensities higher than the maximal intensity of photolimitation (120μmol PhotonPAR.m−2.s−1). No hysteresis effect was observed as light intensities were shifted once and reverted to their original values. These results extend the literature regarding photoacclimation dynamics of antenna size and photosynthetic apparatus. They are well-suited to calibrate photoacclimation models and can provide valuable insight into the strategies to implement for culture scale-up, fed-batch, and semi-continuous processes.

Decaffeination of yerba mate (Ilex paraguariensis) by pressurized liquid CO2 extraction: A feasible process?

This work introduces a pumpless high-pressure Soxhlet cross-current solid-liquid extraction method using liquid CO2 and hydrated ethanol for studying the decaffeination of yerba mate. By combining experimental results with thermodynamic modelling, a comprehensive evaluation of the impact of the co-solvent composition is achieved. It is observed that an ethanol/water mixture with a specific composition of 85 wt% is optimal under mild operating conditions (283 K and 4.5 MPa) for extracting caffeine from chopped yerba mate leaves with a negligible co-extraction of caffeoyl derivative antioxidants. The obtained selectivity, together with the phase equilibrium simulation, provide evidence of the significant potential of liquid CO2 extraction as a decaffeination alternative for yerba mate. Thus, high-pressure Soxhlet extraction serves as simple technique to access valuable experimental information with potential for the conceptual design of further scalable semi-continuous processes.

Improved organic matter biodegradation through pulsed H2 injections during in situ biomethanation

During in situ biomethanation, microbial communities can convert complex Organic Matter (OM) and H2 into CH4. OM biodegradation was compared between Anaerobic Digestion (AD) and in situ biomethanation, in semi-continuous processes, using two inocula from the digester (D) and the post-digester (PoD) of an AD plant. The impact of H2 on OM degradation was assessed using a fractionation method. Operational parameters included 20 days of hydraulic retention time and 1.5 gVS.L−1.d−1 of organic loading rate. During in situ biomethanation, 485 NmL of H2 were injected for each feeding (3 times a week). Maximum organic COD removal was 0.6 gCOD in AD control and at least 1.6 gCOD for in situ biomethanation. Therefore, COD removal was 2.5 times higher with H2 injections. These results bring out the potential of H2 injections during AD, not only for CO2 consumption but also for better OM degradation.

Valorisation of industrial hemp (Cannabis sativa L.) residues and cheese whey into volatile fatty acids for single cell protein production

The production of single cell protein (SCP) using lignocellulosic materials stands out as a promising route in the circular bioeconomy transition. However, multiple steps are necessary for lignocellulosics-to-SCP processes, involving chemical pretreatments and specific aerobic cultures. Whereas there are no studies that investigated the SCP production from lignocellulosics by using only biological processes and microbial biomass able to work both anaerobically and aerobically. In this view, the valorisation of industrial hemp (Cannabis sativa L.) biomass residues (HBRs), specifically hurds and a mix of leaves and inflorescences, combined with cheese whey (CW) was investigated through a semi-continuous acidogenic co-fermentation process (co-AF). The aim of this study was to maximise HBRs conversion into VFAs to be further used as carbon-rich substrates for SCP production. Different process conditions were tested by either removing CW or increasing the amount of HBRs in terms of VS (i.e., two and four times) to evaluate the performance of the co-AF process. Increasing HBRs resulted in a proportional increase in VFA production up to 3115 mg HAc L−1, with experimental production nearly 40% higher than theoretical predictions. The synergy between HBRs and CW was demonstrated, proving the latter as essential to improve the biodegradability of the former. The produced VFAs were subsequently tested as substrates for SCP synthesis in batch aerobic tests. A biomass concentration of 2.43 g TSS L−1 was achieved with a C/N ratio of 5.0 and a pH of 9.0 after two days of aerobic fermentation, reaching a protein content of 42% (g protein per g TSS). These results demonstrate the overall feasibility of the VFA-mediated HBR-to-SCP valorisation process.

Purifying High-Purity Copper via Semi-Continuous Directional Solidification: Insights from Numerical Simulations

High-purity copper is essential for fabricating advanced microelectronic devices, particularly integrated circuit interconnects. As the industry increasingly emphasizes scalable and efficient purification methods, this study investigates the multi-physics interactions during the semi-continuous directional solidification process, utilizing a Cu-1 wt.%Ag model alloy. Coupled simulation calculations examine the spatial distribution patterns of the impurity element silver (Ag) within semi-continuously solidified ingots under varying pulling rates and melt temperatures. The objective is to provide technical insights into the utilization of the semi-continuous directional solidification method for high-purity copper purification. The findings reveal that increasing the pulling rate and melt temperature leads to a downward shift in the solid–liquid interface relative to the mold top during processing. Alongside the primary clockwise vortex flow, a secondary weak vortex emerges near the solid–liquid interface, facilitating the migration of the impurity element Ag toward the central axis and amplifying radial impurity fluctuations. Furthermore, diverse pulling rates and melt temperature conditions unveil a consistent trend along the ingot’s height, which is characterized by an initial increase in average Ag content, followed by stabilization and then a rapid ascent during the late stage of solidification, with higher pulling rates and melt temperatures expediting this rapid ascent. Leveraging these insights, a validation experiment using 4N-grade recycled copper in a small-scale setup demonstrates the effectiveness of the semi-continuous directional solidification process for high-purity copper production, with copper samples extracted at 1/4 and 3/4 ingot heights achieving a 5N purity level of 99.9994 wt.% and 99.9993 wt.%, respectively.

Converting kitchen waste into value-added fertilizer using thermophilic semi-continuous composting-biofiltration two-stage process with minimized NH3 emission

Thermophilic semi-continuous composting (TSC) is effective for kitchen waste (KW) treatment, but large amounts of NH3-rich odorous gas are generated. This study proposes a TSC-biofiltration (BF) two-stage process. Compost from the front-end TSC was used as the packing material in the BF to remove NH3 from the exhaust gas. The BF process was effective in removing up to 83.7 % of NH3, and the NH3 content was reduced to < 8 ppm. Seven days of BF improved the quality of the product from TSC by enhancing the germination index to 134.6 %, 36.5 % higher than that in the aerated-only group. Microbial community analysis revealed rapid proliferation and eventual dominance in the BF of members related to compost maturation and the nitrogen cycle from Actinobacteria, Proteobacteria, Chloroflexi, and Bacteroidetes. The results suggest that the TSC-BF two-stage process is effective in reducing NH3 emissions from TSC and improving compost quality.

Kinetics of Vegetable Oils (Rice Bran, Sunflower Seed, and Soybean) Extracted by Pressurized Liquid Extraction in Intermittent Process

The research focuses on optimizing vegetable oil production processes for human consumption, emphasizing green and efficient extraction methods using renewable solvents with minimal toxic residues. Pressurized liquid extraction (PLE), especially with ethanol, is studied for its efficiency and low solvent usage in intermittent processes. By evaluating extraction parameters and kinetics, the study aims to determine optimal conditions for higher extraction rates and yields, providing insights into production costs and other factors. Specifically, the research examines the behavior of extraction kinetics for vegetable oils like rice bran, sunflower seeds, and rolled soybeans. It also seeks to determine mass diffusivity in semi-continuous processes and to model PLE in intermittent processes using Fick’s Law and Mathematica Wolfram Software v11.2. The effective diffusivity (Deff) for rice bran oil in pressurized ethanol varied between 13.09 and 15.70 × 10−12 m2/s, and the Deff value of sunflower seed oil was between 8.10 and 12.60 × 10−12 m2/s. For rolled soybean oil, the Deff value ranged from 17.25 to 31.29 × 10−12 m2/s. The mass diffusivity values of vegetable oils in pressurized ethanol remained within the same order of magnitude. The mass diffusivity for PLE in an intermittent process presented values of 5.97 × 10−12 m2/s for rice bran oil with 3 extraction cycles. The Deff value for sunflower seed oil in pressurized ethanol was 1.38 × 10−12 m2/s, with 4 cycles, and for rolled soybeans, the Deff value was 1.77 × 10−12 m2/s in 3 cycles. The Deff value found in the intermittent extraction process was lower than that in the semi-continuous process. The total solvent renewal in the semi-continuous extraction process significantly impacted the diffusivity values for all extracted oils, as this process utilizes much more solvent compared to the intermittent process for all matrices studied. Various factors, including geometry, average particle diameter, extraction temperature, and rinse solvent volume, can affect the differences in curve behavior between the semi-continuous and intermittent processes. Despite these factors, the intermittent process is considered more viable for implementation due to its favorable economic and environmental characteristics, primarily because it requires a much smaller amount of solvent.

Semi-continuous mesophilic anaerobic digestion of date palm (Phoenix dactelifyra L.) leaflets of the H'mira cultivar from the Adrar region of Southern Algeria using an alkaline pre-treatment

This research paper aim to investigate the enhancement potential of mesophilic Anaerobic Digestion (AD) of Algerian date palm (Phoenix dactylifera L.) leaflets from H'mira cultivars using an alkaline pretreatment approach. The experiment was conducted for the first time in semi-continuous digesters. NaOH was applied at various percentages (6 %, 12 % and 18 %) to chemically pretreat the substrate for 5 days at 37 °C. The chemical pretreatment results were interpreted for the first time with in-depth FTIR spectroscopic analyses. The Hydraulic Retention Time (HRT) was fixed at 15 days, and the Organic Loading Rate (OLR) at 2 g MO/L/day. The results showed that the methane (CH4) production values were stabilized with a clear distinction at averages of 211.85, 177.26, 143.36 and 123.07 ml of CH4/day, i.e. a CH4 yield of 105.92, 88.63, 71.68 and 61.53 ml of CH4/gVS/day for the reactors containing substrates pre-treated with 12 %, 6 %, 18 % NaOH and the substrate without pre-treatment respectively. Compared to the substrate without pre-treatment, the CH4 production rates were improved 1.72, 1.44 and 1.16 times for the reactors containing 12 %, 6 % and 18 % NaOH respectively. These findings were perfectly in accordance with FTIR spectroscopy results. These findings demonstrate that the semi-continuous AD process can be an attractive energy recovery solution from such waste compared to batch digesters, (on one day, it produce 77–105 % of the CH4 produced during 21–55 days in batch digesters), as well as the importance of adequate pre-treatment prior to the AD. FTIR Spectroscopic analysis technology can also be widely used to analyze pre-treatment data for lignocellulosic biomass, as it gives very encouraging results.

Minimizing total annualized cost per tonne of feed processed of a semicontinuous distillation process utilizing data-driven model predictive control

Semicontinuous distillation is a separation technique used to purify multicomponent mixtures with low to medium throughput. This research addresses the problem of designing a Data-driven Model Predictive Control (MPC) approach that enables minimizing the Total Annualized Cost (TAC) of the semicontinuous process per tonne of feed processed while maintaining the required product purity. In lieu of typically unavailable first principles models, the manuscript demonstrates the implementation of data-driven technique using data collected from an Aspen Plus Dynamics simulation as a test bed. A subspace model identification technique is adapted to develop a multi-model framework to capture the dynamic behavior of the process and then utilized within a Shrinking Horizon MPC (SHMPC) scheme, to achieve the required objective. The simulation results demonstrate a lowering of the TAC/tonne of feed by 11.4% compared to the traditional PI setup used in the previous studies.

The Effect of Feeding Sequence on the Structure and Properties of the Ethylene/1-Octene Copolymer in the Semi-Continuous Polymerization Reaction System.

The performance of ethylene/1-octene copolymer primarily depends on the microstructure of the polymer chain. This study employed a new method to control the inter-distribution of hexyl chain branches directly on the backbone of the ethylene/1-octene copolymer. Three ethylene/1-octene copolymers with different inter-distributions of hexyl chain branches were synthesized using [Me2Si(C5Me4) (NtBu)] TiCl2 (Ti-CGC) by different feeding sequences in the semi-continuous polymerization reaction system. The three copolymers were named according to the feeding sequence of the materials: ethylene/1-octene/Ti-CGC (EOC), 1-octene/Ti-CGC/ethylene (OCE), and ethylene/Ti-CGC/1-octene (ECO), respectively. The structure and properties of the copolymers were characterized using HT-GPC, 13C-NMR, DSC, WAXD, DMA, MI, and Uniaxial Tension Test. The results showed that the feeding sequence greatly affected the comonomer distribution of the molecular chains, molecular weight, molecular weight distribution, and chemical composition of the copolymers, consequently influencing their thermal performance and mechanical properties. Thus, it is probable that one could obtain an ethylene/1-octene copolymer with designed properties by controlling the feeding sequence during the ethylene/1-octene semi-continuous copolymerization process.

Thermally enhanced solid-liquid separation process in food waste biorefinery: modelling the anaerobic digestion of solid residues.

The biochemical valorization potential of food waste (FW) could be exploited by extracting decreasing added-value bio-based products and converting the final residues into energy. In this context, multi-purpose and versatile schemes integrating thermal and biochemical conversion processes will play a key role. An upstream thermal pretreatment + solid-liquid separation unit was here proposed to optimize the conversion of the liquid fraction of FW into valuable chemicals through semi-continuous fermentation process, and the conversion of the residual solid fraction into biomethane through anaerobic digestion. The solid residues obtained after thermal pretreatment presented a higher soluble COD fraction, which resulted in higher methane production with respect to the raw residues (0.33 vs. 0.29 Nm3CH4 kg-1VSfed) and higher risk of acidification and failure of methanogenesis when operating at lower HRT (20d). On the contrary, at HRT = 40 d, the pretreatment did not affect the methane conversion rates and both tests evidenced similar methane productions of 0.33 Nm3CH4 kg-1VSfed. In the reactor fed with pretreated residue, the association of hydrogenotrophic methanogens with syntrophic bacteria prevented the acidification of the system. Modelling proved the eligibility of the FW solid residues as substrates for anaerobic digestion, given their small inert fractions that ranged between 0% and 30% of the total COD content.

Coupling anaerobic co-digestion of winery waste and waste activated sludge with a microalgae process: Optimization of a semi-continuous system

Wine production represents one of the most important agro-industrial sectors in Italy. Wine lees are the most significant waste in the winery industry and have high disposal and storage costs and few applications within the circular economy. In this study, anaerobic digestion and a microalgae coupled process was studied in order to treat wine lees and waste activated sludge produced within the same facility, with the aim of producing energy and valuable microalgae biomass that could be processed to recover biofuel or biostimulant. Chlorella vulgaris was cultivated on liquid digestate in a semi-continuous system without biomass recirculation. The best growth and phytoremediation performance were achieved applying a hydraulic retention time (HRT) of 20 days with a stable dry weight, lipid and protein storage of 1.85 ± 0.02 g l−1, 33.48 ± 7.54 % and 57.85 ± 10.14 % respectively. Lipid characterization highlighted the potential use in high quality biodiesel production, according to EN14214 (<12 % v/v linolenic acid). The microalgae reactor’s liquid output showed high removal of ammonia (95.72 ± 2.10 %), but low organic soluble matter reduction. Further semi-continuous process optimization was carried out by increasing the time between digestate feeding and biomass recovery at HRT 10. These operative changes avoided biomass wash-out and provided a stable phytoremediation of the digestate with 84.58 ± 4.02 % ammonia removal, 33.01 ± 1.44 % sCOD removal, 38.06 ± 2.65 % of polyphenols removal.

Investigation and Optimization of Operational Conditions of Anaerobic Digestion Process for Enhanced Biogas Production Yield in a CSTR Using RSM

In this study, pilot‐scale experiments were performed on the anaerobic digestion (AD) in a semicontinuous process using a continuously stirred tank reactor to determine the effects of organic loading rate (OLR), temperature, and mixing levels on biogas production yield. Fresh cow manure was considered the input feedstock of this study due to its high production volume. Response surface methodology (RSM) was employed to design and analyze experiments to optimize OLR, temperature, and mixing intensity in biogas production. The central composite design was applied as a RSM optimization tool. Four cubic mathematical models were derived to predict the responses. The optimization study was carried out to identify the highest yields achievable when temperature and mixing factors are minimized. Temperature and OLR have been found to have a greater influence on biogas production compared to mixing intensity. The AD process is significantly influenced by temperature. Variations in temperature, specifically near 40 and 55°C, lead to an increase in the rate of biogas production. Therefore, the best temperatures for biogas production rate are near 40 and 55°C. The results of the performed optimizations suggest to adopt OLR values range of 1.6–2.5 kgVSCow manure/m3 · day, and 2.5–3.4 kgVSCow manure/m3 · day in the case of temperature ranges 20–40°C and 40–55°C, respectively.

Enhancing small-scale acetification processes using adsorbed Acetobacter pasteurianus UMCC 2951 on κ-carrageenan-coated luffa sponge.

This study explored the utilization of luffa sponge (LS) in enhancing acetification processes. LS is known for having high porosity and specific surface area, and can provide a novel means of supporting the growth of acetic acid bacteria (AAB) to improve biomass yield and acetification rate, and thereby promote more efficient and sustainable vinegar production. Moreover, the promising potential of LS and luffa sponge coated with κ-carrageenan (LSK) means they may represent effective alternatives for the co-production of industrially valuable bioproducts, for example bacterial cellulose (BC) and acetic acid. LS and LSK were employed as adsorbents for Acetobacter pasteurianus UMCC 2951 in a submerged semi-continuous acetification process. Experiments were conducted under reciprocal shaking at 1 Hz and a temperature of 32°C. The performance of the two systems (LS-AAB and LSK-AAB respectively) was evaluated based on cell dry weight (CDW), acetification rate, and BC biofilm formation. The use of LS significantly increased the biomass yield during acetification, achieving a CDW of 3.34 mg/L versus the 0.91 mg/L obtained with planktonic cells. Coating LS with κ-carrageenan further enhanced yield, with a CDW of 4.45 mg/L. Acetification rates were also higher in the LSK-AAB system, reaching 3.33±0.05 g/Ld as opposed to 2.45±0.05 g/Ld for LS-AAB and 1.13±0.05g/Ld for planktonic cells. Additionally, BC biofilm formation during the second operational cycle was more pronounced in the LSK-AAB system (37.0±3.0 mg/L, as opposed to 25.0±2.0 mg/L in LS-AAB). This study demonstrates that LS significantly improves the efficiency of the acetification process, particularly when enhanced with κ-carrageenan. The increased biomass yield, accelerated acetification, and enhanced BC biofilm formation highlight the potential of the LS-AAB system, and especially the LSK-AAB variant, in sustainable and effective vinegar production. These systems offer a promising approach for small-scale, semi-continuous acetification processes that aligns with eco-friendly practices and caters to specialized market needs. Finally, this innovative method facilitates the dual production of acetic acid and bacterial cellulose, with potential applications in biotechnological fields.

Separation of the heme protein cytochrome C using a 3D structured graphene oxide bionanocomposite as an adsorbent.

Proteins are of great importance for medicine and the pharmaceutical and food industries. However, proteins need to be purified prior to their application. This work investigated the application of a hydrogel bionanocomposite based on agar and graphene oxide (GO) for capturing cytochrome C (Cyto C) heme protein by adsorption from aqueous solutions with other proteins. Although applications of GO-based materials in adsorption are widely studied, the focus on semi-continuous processes remains limited. Adsorption experiments were carried out in batch and fixed bed columns. The effect of pH and ionic strength on adsorption was investigated, and there is evidence that electrostatic interactions between Cyto C and the nanocomposite were favoured at pH = 7; the adsorption capacity decreased as NaCl and KCl concentrations increased, ascribed to the weak electrostatic interaction between the protein and GO active sites in the bionanocomposite. All adsorption isotherm models (Langmuir, Freundlich, Sips) used gave suitable adjustments to the equilibrium experimental data and the kinetic models applied. The maximum adsorption capacity predicted by the Langmuir isotherm was ∼400 mgCytoC gadsorbent,dry-1, and the adsorption thermodynamics indicated a physisorption process. Tests were performed to evaluate the co-adsorption in batch, and the composite was effective in adsorbing Cyto C in solution with bovine serum albumin (BSA) and L-phenylalanine. Fixed bed tests were performed, and although protein adsorption onto nanoparticles can be challenging, the Cyto C adsorbed could be successfully recovered after desorption. Overall, the GO-based hydrogel was an effective method for cytochrome C adsorption, exhibiting a notorious potential for applications in protein separation processes.

Electrocoagulation Technique for Treating Swine Slaughterhouse Wastewater from Batch to Semicontinuous Operation Mode

In this study, industrial swine slaughterhouse wastewater was treated by electrocoagulation process using batch and semicontinuous operation systems. Electrochemical technique was carried out in batch operation mode during 2.5 h applying different current densities in sulfate and chloride media. After finding the best operating parameters in batch mode (lab-scale), the process was transferred to a semicontinuous pre-pilot scale process using a filter-press FM01-LC type electrochemical reactor fitted with flat plate aluminum electrodes. In this stage, distinct current densities and mean linear flow rates were assessed.Total organic carbon, chemical oxygen demand, total phosphorus, total nitrogen, and potassium among other parameters were analyzed during both treatments. The industrial swine slaughterhouse wastewater contained TOC 333 mg L–1, COD 1765 mg L–1, TP 13.55 mg L–1, TN 327 mg L–1, K 45 mg L–1, turbidity 102 NTU, color –absorbance 0.90 A.U. at 415 nm–, conductivity 1.9 mS cm–1, and pH 6.9. The highest TOC removal efficiency (72.7%), in semicontinuous process, was found at j = 25 mA cm-2 and ur = 0.64 cm s-1 with an energy consumption of 19.80 kW h m-3. Residual COD and TP concentrations met the international standard limits. Moreover, complete discoloration and disinfection were achieved. EDXRF, SEM, EDAX, XRD, and FTIR analyzes indicate pollutants were removed by adsorption on aluminum/iron hydroxides/oxyhydroxides.