Specific Reaction Time Research Articles

Optimization of synthesis parameters for polyamide 610: Strategic tailoring for superior latent heat performance

The study systematically optimizes the synthesis of polyamide 610 with the aim of improving latent heat and melting temperature to meet the demanding requirements of high-temperature heat storage applications using Response Surface Methodology (RSM). The results clarify the critical impact of reaction times, washing solvents, and molar ratios on these vital thermal characteristics. Samples exhibiting exceptional latent heat capacities at various mole ratios were further analyzed using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD). The TGA assessments were instrumental in determining the thermal degradation behaviors of the materials. At the same time, The DSC analysis was used for the determination of thermal properties of the materials, FTIR provided detailed insights into their molecular structures, and XRD elucidated the crystalline structure of the materials. The findings reveal that a specific mole ratio is essential for achieving superior thermal properties, indicative of the polymer's resilience and structural stability. It was evident that samples with a balanced molar ratio (1:1) and specific reaction time (60 min) showed the best latent heat, surpassing 80 J g-1, and melting temperatures up to 210 °C. A notable aspect of this research is the use of Sebacic Acid instead of the conventional Sebacoyl Chloride for synthesizing polyamide 610. The choice of Sebacic Acid was made due to its lower toxicity and the fact that its byproducts are easier to remove than those from sebacoyl chloride, which produces hydrochloric acid as a byproduct. The presence of HCL can lead to side reactions and negatively impact the reaction process. By using Sebacic Acid, we reduce the risk of such contaminants, thereby enhancing the thermal stability and performance of polyamide 610. This greener approach not only aligns with sustainable practices but also has significant implications for the performance of the polymer. In addition, the integration of RSM with comprehensive characterization techniques has been pivotal in elucidating the critical influence of synthesis parameters on material properties. This enhanced understanding holds the potential for significant contributions to the development of advanced materials for latent heat storage applications, combining sustainability with high performance.

Preparation of novel zwitterionic polysulfone ultrafiltration membranes for the dual-enhanced antifouling and antibacterial properties by in-situ one pot crosslinking reaction

Zwitterionic polysulfone (PSf) ultrafiltration membranes were fabricated by non-solvent phase separation (NIPS) method. Herein, a casting solution at 45 °C was developed by using chloromethylated polysulfone (CMPSf), N, N-dimethylacetamide (DMAc) as a solvent, 4-amino-benzenesulfonic acid monosodium salt (ABS) as a cross-linking agent, and Na2CO3 as an acid binder. Simultaneously, the occurrence of the electrophilic substitution reaction between ABS and CMPSf caused the formation of ABS grafting CMPSf (CMPSf-g-ABS). After a specific reaction time, the casting solution was applied to cast membranes, which were subsequently submerged in coagulation bath. A zwitterionic ultrafiltration (ZUF) membrane was obtained using NIPS following the treatment of hydrochloric acid (HCl) solution (1 M mol). Because of the formation of cross-linked CMPSf-g-ABS, the results revealed that the casting solution's viscosity increased sharply from 425.4 mPa s at the initial stage (0 h) to 4810.8 mPa s (22 h). Interestingly, the morphology of the membranes with an asymmetric finger-like structure at 0 h gradually transformed to a gradient sponge-like structure after 22 h. Specifically, the ZUF membrane (M22-H) with the gel fraction of 72.1% procured after the reaction of 22 h demonstrated a low water contact angle (40.17°) and a high pure water permeance (420.4 L m−2 h−1 bar−1). The M22-H also exhibited a high flux recovery rate (FRR) (90.2%), bovine serum albumin (BSA) rejection (>95%), and Escherichia coli (E. coli) antibacterial rate (96.2%). The surface of the ZUF membrane with numerous zwitterionic groups enhances the hydration layer's energy (i region <16 nm) and creates a thick hydration layer (ii region >16 nm), causing a significant improvement in the antifouling performance. This research opens new avenues for preparing zwitterionic functional membranes.

Parameters Synthesis of Na-Magadiite Materials for Water Treatment and Removal of Basic Blue-41: Properties and Single-Batch Design Adsorber

Na-magadiite materials were prepared from a gel containing a silica source, sodium hydroxide, and water via hydrothermal treatment at different temperatures (130 °C to 170 °C) and periods of time (1 day to 10 days). In this study, four silica sources were selected (fumed silica, colloidal silica, Ludox HS-40%, and Ludox AS-40%). Variable conditions such as sodium hydroxide and water contents were explored at a specific temperature and reaction time. The obtained materials were characterized by using X-ray diffraction (XRD), thermogravimetry differential thermal analysis TG-DTA, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Fourier Transform Infrared spectroscopy (FTIR), solid 29Si magic angle spinning magnetic nuclear resonance (MAS MNR, and nitrogen adsorption isotherms. A pure Na-magadiite phase was obtained from the four silica sources at a synthesis temperature of 150 °C after a period of one to two days with a characteristic basal spacing of 1.54 nm. At a longer reaction time of 3 days and a higher temperature of 170 °C, Na-kenyaite with a basal spacing of 2.01 nm was achieved, in addition to a quartz phase. The content of water or sodium hydroxide in the gel affected the nature of the prepared phases. A cauliflower-like morphology was obtained from colloidal silica sources, while a different morphology was achieved using solid fumed silica. The 29Si solid NMR confirmed the presence of Q3 and Q4 silicon sites in the Na-magadiite materials. The optimal Na-magadiite materials at 150 °C for 2 days were assessed for their ability to remove Basic Blue-41 dye from artificially contaminated aqueous solution. The Langmuir equation was used to estimate the maximum removal capacity. A maximum removal capacity of 219 mg/g was achieved using Na-magadiite prepared from a Ludox-HS40% silica source, and a maximum removal capacity of 167 mg/g was observed for Na-magadiite prepared from fumed silica. Basic Blue-4’s removal percentage was enhanced at basic pH levels (8 to 10) to a maximum of 95%. These materials could be regenerated for seven cycles of reuse with a reduction of 27 to 40% of the original values. Therefore, Na-magadiite materials are promising and efficient removal agents for the removal of Basic Blue-41 from effluents.

JudgED: Comparison between Kickboxing Referee Performance at a Novel Serious Game for Judging Improvement and at World Championships

The particular responsibility of referees in combat sports lies in their decision-making to enforce the rules of the sport, which requires considerable experience and a multitude of skills, including perception, categorization, memory processing, and information integration. As a cost-effective alternative to in-tournament training, this research aims to evaluate the novel video-based serious game called “JudgED” to train martial arts referees’ decision-making processes through immediate feedback. The effectiveness of the JudgED game was assessed by (a) measuring decision accuracy and specific reaction time, (b) calculating a theoretical probability of correct scoring, and (c) comparing these results with real competition judging agreement data. A field study was conducted to analyze the performance of 16 kickboxing referees. The study involved two video-based tests in the serious game. The performance data for JudgED were obtained via a procedure that compares the players’ inputs in the serious game with expert-defined decisions. The results were compared to real-competition data gathered through qualitative analysis of kickboxing fights (n = 400 fights/1200 bouts) at the WAKO World Championships 2021. The findings showed an average decision accuracy of 43.011% and an average reaction time of 1.022 s. For further comparison, binominal distribution for the probability of correct final decisions (between 15.3% and 67.2%) in JudgED and Fleiss’ Kappa interrater reliability for JudgED (Ring: κ = 0.371; Tatami: κ = 0.398; p &lt; 0.001) and tournament decisions (by bout: κ = 0.114; by fight κ = 0.063; by outcome κ = 0.166; p &lt; 0.001) were calculated. The results suggest that more training is required to improve referee decision accuracy, and JudgED bears the potential to work as a suitable supporting system.

Can Qigong Be a Tool to Assist Students in Handling COVID-19's Resulting Academic Stress?

The recent COVID-19 pandemic has increased students' stress as they may feel under increased pressure to have a good performance and compensate for the disruption to their education. Improving attention levels and learning capacity may assist in ameliorating academic performance. Qigong is a traditional Chinese medicine technique that appears to have positive effects on the management of mental health and may provide tools for coping with stressful situations. This paper explores data obtained while conducting a previous study and includes an excess of data from a total of 44 participants who were previously divided into an experimental Qigong group and a sham Qigong control group. The improvements in specific auditory processing and reaction times may indicate benefits in attention and learning capacity. These improvements were more pronounced in the experimental Qigong group compared to the sham Qigong group. Qigong may be able to assist in improving students' academic performance and can be easily integrated into physical education classes. It could also assist students to cope with the increased academic pressure resulting from the COVID-19 pandemic context.

Deconvolution of photoluminescence spectra and electronic transition in carbon dots nanoparticles from microcrystalline cellulose

Carbon dots (CDs) are nanomaterials with promising applications in several areas such as optoelectronics and biomedicine due to their low toxicity and strong luminescence intensity. Understanding the emission and bandwidth of the fluorescence spectrum is still a challenge in the scientific community due to the dependence of emission on the excitation wavelength. In this work, the photoluminescence properties of carbon dots obtained from microcrystalline cellulose (MCC) were studied. The optical properties were studied through measurements of photoluminescence (PL), photoluminescence excitation (PLE), and absorption. Systematic adjustments were made through Gaussian deconvolution of the PL spectrums and the coupling between electronic states was analyzed through PLE and optical absorption measurements. From the Gaussian adjustments, bandwidth values of ∼25 nm and ∼100 nm were found for the emission associated with the core and the surface states respectively, these values are consistent with the bandwidth of the PLE spectra with tuned detection in these states. As evidenced by the results, there are contributions from the core and surface functional groups in the luminescence emission of CDs. Furthermore, with recent analyzes that attribute the radiative emission of CDs only to the surface trap states, we observed that the core present emission and absorption of light for samples with specific pH and reaction times. These results should contribute to the understanding of the electronic transitions of CDs for applications related to the luminescent optical properties of these nanomaterials.

Poststroke action slowing: Motor and attentional impairments and their imaging determinants. Evidence from lesion-symptom mapping, disconnection and fMRI activation studies

Background and objectivesAlthough action slowing is the main cognitive impairment in stroke survivors, its mechanisms and determinants are still poorly understood. The objectives of the present study were to determine the mechanisms of post-stroke action slowing (using validated, highly specific simple reaction time (SRT) and tapping tests) and identify its imaging determinants (using multivariate lesion-symptom mapping (mLSM)). MethodsAction speed in the GRECogVASC cohort was assessed using finger tapping and SRT tests performed with both hands and analyzed using previously validated indices. Imaging determinants were identified using validated mLSM analyses and disconnection analysis and compared to those of an fMRI activation meta-analytic database. ResultsBoth the tapping time and SRT were 10.7% slower for the 394 patients (p = 0.0001) than for the 786 controls, without a group × test interaction (p = 0.2). The intra-individual distribution curve was characterized by a rightward shift with an unaltered attentional peak. The mLSM analyses showed tapping to be associated with lesions in the frontostriatal tract (p = 0.0007). The SRT was associated with lesions in the frontostriatal tract (p = 0.04) and the orbital part of F3 (p = 0.0001). The SRT-tapping index was associated with lesions in the orbital part of F3 (p = 0.0001). All lesions were located in the right hemisphere only and were responsible for the disconnection of several structures involved in motor preparation, initiation, and speed. A comparison with fMRI activation meta-analytic data highlighted mostly the same regions, including the orbital part of F3, the ventral and dorsal parts of F1, and the premotor and cingulate regions in the right hemisphere. DiscussionOur results confirm the marked impairment of action speed in stroke and show that the primary mechanism is motor slowing and that it is related to lesions in the right frontostriatal tract. A deficit in sustained alertness accounted for action slowing in the subgroup with lesions in the right orbital part of F3. Our SRT and mLSM results were in accordance with the fMRI activation data. Thus, stroke induces slowing in the broad network associated with SRT tasks by disrupting the frontostriatal tract and, to a lesser extent, other sites involved in attention.

How shared goals shape action monitoring

Cooperation triggers expectations on our partners' contributions to achieve a common goal. A partner, however, may sometimes violate such expectations, driving us to perform immediate adjustments. What neurophysiological mechanisms support these adaptations? We tested the hypothesis of an interaction-specific brain system that can decode a partner's error and promote adaptive responses when cooperating toward a shared goal. During functional magnetic resonance imaging, the participants played short melodies with a virtual partner by performing one note each in turn-taking. A colored cue indicated which melody they had to execute at each trial, thus generating expectations on what notes the partner would play. The participants also performed the task in a perceptually matched Non-Interactive context. The results showed that task interactivity modulates the brain responses to a partner's error in dorsal fronto-temporoparietal and medial cingulo-opercular networks. Multivariate pattern analysis revealed that these neural activations reflect deep decoding of the partner's mistake. Within these networks, the automatic tendency to correct the partner's errors, as indexed by specific reaction times adaptations, depended on the activity of a right-lateralized fronto-opercular system that may enable mutual support during real-life cooperation. Future studies may unveil the role of this putative "interaction monitoring" brain system in social dysfunctions and their motor foundations.

Construction of Electrochemical Aptamer Sensor Based on Pt-Coordinated Titanium-Based Porphyrin MOF for Thrombin Detection.

In this work, a Pt-coordinated titanium-based porphyrin metal organic framework (Ti-MOF-Pt) was prepared by embedding single-atom Pt through strong interactions between the four pyrrole nitrogen atoms in the rigid backbone of the porphyrin. The synthesized Ti-MOF-Pt was characterized by TEM, XRD, FTIR and BET. Then, the Ti-MOF-Pt has been used for glassy carbon electrode surface modification and consequently used for construction of a thrombin aptamer sensor. The high surface area provides by MOF and excellent electrochemical property provided by Pt enhance the sensing performance. After optimization of amount of aptamer, hybridization time and specific reaction time, the fabricated aptamer sensor exhibited a linear relationship with the logarithm of the thrombin concentration in the range of 4 pM to 0.2 μM. The detection limit can be calculated as 1.3 pM.

Hydrothermal synthesis of carbon quantum dots with size tunability via heterogeneous nucleation.

Hydrothermal synthesis has been extensively utilized for fabricating carbon quantum dots (CQDs). Generally, the average sizes of the CQDs are controlled by using specific precursor concentrations, processing temperatures, and reaction times. In our study, the average size of CQDs can simply be controlled by using a different filling volume of sucrose solution in the hydrothermal reactor while keeping the other experimental parameters constant. If homogeneous nucleation plays a major role in the hydrothermal synthesis, the CQDs synthesized by using different filling volumes should have relatively the same size. Nonetheless, we found that the average size of CQDs is inversely correlated with the filling volumes. Particularly, for the hydrothermal syntheses with the filling volumes of 20%, 50%, and 80%, the average size of the CQDs is 15, 13, and 4 nm, respectively. Therefore, the hydrothermal synthesis of CQDs with size-tunability can be achieved by the heterogeneous process associated with the total surface areas between the precursor and reactor.

Impacts of Green Synthesis Process on Asymmetric Hybrid PDMS Membrane for Efficient CO2/N2 Separation.

The effects of green processes in hybrid polydimethylsiloxane (PDMS) membranes on CO2 separation have received little attention to date. The effective CO2 separation of the membranes is believed to be controlled by the reaction and curing process. In this study, hybrid PDMS membranes were fabricated on ceramic substrates using the water-in-emulsion method and evaluated for their gas transport properties. The effects of the tetraethylorthosilicate (TEOS) concentration and curing temperature on the morphology and CO2 separation performance were investigated. The viscosity measurement showed that, at specific reaction times, it is benefit beneficial to fabricate the symmetric hybrid PDMS membranes with a uniform and dense selective layer on the substrate. Moreover, the a high TEOS concentration can decrease the reaction time and obtain create the a fully crosslinked structure, allowing more efficient CO2/N2 separation. The separation performance was furtherly improved with in the membrane prepared at a high curing temperature of 120 °C. The developed membrane shows excellent CO2/N2 separation with a CO2 permeance of 27.7 ± 1.3 GPU and a CO2/N2 selectivity of 10.3 ± 0.3. Moreover, the membrane shows a stable gas separation performance of up to 5 bar of pressure.

Reproductivity And Validity Analysis Of Badminton Player Cognitive Performance Using Badminton Reaction Inhibition Test (BRIT)

The purpose of this study was to analyze the reproducibility and validity of the Badminton Reaction Inhibition Test (BRIT) or the Badminton Reaction Barrier Test. BRIT measures four components: general-domain reaction time, badminton-specific reaction time, general-domain inhibition control, and badminton-specific inhibition control. Fifteen male national badminton athletes and nine non-national badminton players in Region 3 Cirebon participated in this study. Five participants were retested within three weeks on a specific badminton component. Reproducibility was acceptable for badminton specific reaction times (ICC = 0.626, CV = 6%) and for badminton specific inhibition controls (ICC = 0.317, CV = 13%). The validity of a good construct was shown in the specific poor reaction time that differentiated between national level athletes and non-national athletes (F = 6.650, p 0.05). Concurrent validity for general-domain reaction times was good, as it was associated with the national rankings for national level athletes (? pro = 0.70, p 0.05). In conclusion, the reproducibility and validity of the control inhibition assessment are not confirmed, however, BRIT appears to be a valid and reproducible measure of reaction time in badminton players. Reaction times as measured by BRIT can provide input for training programs aimed at improving badminton player performance.

The “implicit” serial reaction time task induces rapid and temporary adaptation rather than implicit motor learning

The serial reaction time task (SRTT) has been widely used to induce learning of a repeated motor sequence without the participants’ awareness. The task has also been of major influence for defining current concepts of offline consolidation after motor learning. The present study intended to replicate previous findings in a larger population of 53 healthy individuals. We were unable to reproduce previous results of online and offline implicit motor learning with the SRTT. Trials with a repeated sequence rapidly induced shorter reaction times compared to random trials, but this improvement was lost in a post-test obtained a few minutes after the training block. Furthermore, no offline consolidation was observed as there was no change in sequence specific reaction time gain between the post-test immediately after training and a re-test obtained 8 h after training. Online or offline learning remained absent when we modulated the number of sequence repetitions, the error levels, and the structure of random sequences. We conclude that the SRTT induces a rapid and temporary adaptation to the sequence rather than learning, since the repeated motor sequence does not seem to be encoded in memory.

Effectiveness of ozone pretreatment on bioconversion of oily bilge water into biopolymer

Oily bilge water (OBW) is complex wastewater generated from ship operation. In the present study, the application of ozonation pretreatment before the sequential batch reactor (SBR) for removing organics and polyhydroxyalkanoates (PHA) production from complex OBW were investigated. OBW was subjected to lab-scale ozone pretreatment under the various experimental conditions such as a specific reaction time (0 min–120 min), inlet ozone dose (0.5 g/L–2.5 g/L) and solution pH (4–8). Pretreatment of OBW by ozone improved biodegradability index (BDI) from 0.36 to 0.52. The GC–MS analysis revealed that the BDI enhancement was due to the formation of water-soluble carboxylic groups after 75 min of ozonation operated at solution pH 6 and 2 g/ L of O3 dose. The CODs removal efficiency was 68 % and 92 % for SBR and ozonized SBR respectively. Also, the biopolymer production rate was increased by 4.5 folds for ozonized SBR as the bioconversion of carboxylic compounds by using a mixed bacterial consortium (MBC) was stress-free. The functional groups and thermal property of the produced PHA were tested by various analytical techniques. These results confirmed that the bioconversion of ozonized OBW into valuable biological polyesters using MBC.

Tracking intermediate performance of vigilant attention using multiple eye metrics.

Vigilance deficits account for a substantial number of accidents and errors. Current techniques to detect vigilance impairment measure only the most severe level evident in eyelid closure and falling asleep, which is often too late to avoid an accident or error. The present study sought to identify ocular biometrics of intermediate impairment of vigilance and develop a new technique that could detect a range of deficits in vigilant attention (VA). Sixteen healthy adults performed well-validated Psychomotor Vigilance Test (PVT) for tracking vigilance attention while undergoing simultaneous recording of eye metrics every 2 hours during 38 hours of continuous wakefulness. A novel marker was found that measured VA when the eyes were open-the prevalence of microsaccades. Notably, the prevalence of microsaccades decreased in response to sleep deprivation and time-on-task. In addition, a novel algorithm for detecting multilevel VA was developed, which estimated performance on the PVT by integrating the novel marker with other eye-related indices. The novel algorithm also tracked changes in intermediate level of VA (specific reaction times in the PVT, i.e. 300-500 ms) during prolonged time-on-task and sleep deprivation, which had not been tracked previously by conventional techniques. The implication of the findings is that this novel algorithm, named "eye-metrical estimation version of the PVT: PVT-E," can be used to reduce human-error-related accidents caused by vigilance impairment even when its level is intermediate.

Removal of Heavy Metals Using Rhamnolipid Biosurfactant on Manganese Nodules

The objective of this study is to identify the feasibility of using rhamnolipid biosurfactant to remediate heavy metals contained in manganese nodules collected from the Clarion-Clipperton Fracture Zone, Pacific Ocean. Deep-sea manganese nodules may represent one of the most important future natural resources for heavy metals due to the depletion of resources on land. Since international marine environment guidelines for deep-sea mining will be set up by international organisations in the 2020s, remediation technologies are urgently required for deep-sea mining tailings. We show that rhamnolipid biosurfactant is an environmentally friendly substance and can be successfully used for the remediation of heavy metals in deep-sea mining tailings under various reaction conditions. Rhamnolipids therefore represent a useful extracting agent for heavy metals in deep-sea mining tailings. The removal of nickel (Ni), copper (Cu), and cadmium (Cd) would be enhanced in the presence of rhamnolipids with specific reaction times and concentrations. Future actual remediation technologies should be developed using rhamnolipid biosurfactant on the basis of these results.

Submersible probe type microbial electrochemical sensor for volatile fatty acids monitoring in the anaerobic digestion process

Abstract: Microbial electrochemical sensor with a more simplified architecture is required in the anaerobic digestion (AD) process for in situ on-line volatile fatty acids (VFAs) monitoring. In this study, a submersible probe type microbial electrochemical sensor was constructed, and the current signal showed a linear relationship with the VFAs concentration (0–200 mM) at the specific reaction time from 10 to 120 min (R2 > 0.96), with the slope increased from 0.87 × 10−3 to 1.70 × 10−3 mA mM −1. The sensor showed a good selectivity when VFAs were co-existed with 2 g/L of additional organic matters (cellulose, yeast extract, peptone, and potassium oleate), and 0.1% formaldehyde. Particular attention should be paid when additional electroactive matter such as Cu(II) as well as high concentration of TAN (above 200 mg/L) was co-existed with VFAs in the digestate. When amending the artificial AD digestate with extra 50 mM NaCl to increase the ionic strength, the current generation increased from 0.064 ± 0.002 to 0.185 ± 0.001 mA (50 mM VFAs at 60 min). The sensor was successfully applied for actual digestate samples detection and the results did not show significance differences with the total VFAs measured by GC. The submersible probe type sensor depicted a good repeatability during one-month operation. This study provides a direct approach based on microbial electrochemical technology for VFAs monitoring in the AD process.

Effect of humic acid on Se and Fe transformations in soil during waterlogged incubation

Humic acid (HA) serves as electron donor and acceptor in the biogeochemical cycle of Fe and Se in soil. In anoxic condition, a series of redox reactions occur, including reductive dissolution of Fe oxides, decomposition of organic matters, and transformation of trace elements. Thus, this study demonstrates the effect of HA on Se and Fe transformations in soil during waterlogged incubation. Soils were incubated under anoxic condition for 56 days, and pH, redox potential (Eh), and Fe and Se concentrations were measured at specific reaction times (days 2, 4, 8, 15, 28, and 56 of incubation). Moreover, sequential extraction and X-ray photoelectron spectroscopy (XPS) were used to obtain Se and Fe transformations, respectively. High resolution transmission electron microscopy (HR-TEM) was used to observe the morphology properties of soil. Results indicated that 4% HA addition decreased the pH and inhibited Eh decline continuously, and HA addition inhibited the Fe and Se release from soil. The Se concentration in soil solution without and with 4% HA addition at the day 15 of incubation were 1.05 mg L−1 and 0.30 mg L−1, respectively. Moreover, the residual Se fraction in soil with HA addition was evidently more than that in soil without HA addition. XPS of Se3d and Fe2p revealed that the binding energy of the main peak shifted to low values and the peak shape varied with the increase in HA addition. XPS2p3/2 and HR-TEM data indicated that the surface structure of Fe oxides in soil varied with the variations in anoxic incubation time and HA addition amount. HA addition would negatively influence Se and Fe release in soil solution and then reduce their bioavailability. This study aids in understanding the environmental behavior changes of Se and Fe when high HA concentrations enter the soils, especially wetland or paddy soil.

The Potential of Bioelectrochemical Sensor for Monitoring of Acetate During Anaerobic Digestion: Focusing on Novel Reactor Design.

Acetate as the dominant fraction of volatile fatty acids (VFAs) is an important intermediate in metabolic pathways of methanogenesis, which could reflect the stability status of anaerobic digestion (AD) process. Bioelectrochemical sensors for environmental or bioprocess monitoring have become increasingly attractive in recent years. Although it was more favorable, several challenges still need to be addressed for acetate detection, including large electrode spacing, low stability, biofouling at the cathode and low detection range. In this study, an innovative biosensor on the basis of a three-chamber microbial electrochemical system was proposed to monitor the acetate during the AD process. In such a system, acetate was first transferred from sample chamber through the anion exchange membrane (AEM) to anode due to the driven force of concentration difference and then oxidized by anodic biofilm as a substrate for the current generation. With such design, the influence of waste properties fluctuation in the cathodic reaction could be avoided. The response of current density to different acetate concentrations was investigated. The selectivity, the influence of the sample temperature and the external resistance were also evaluated. The correlation (R2 > 0.99) between the current densities and acetate concentrations (up to 160 mM) was established at specific reaction time (from 2 to 5 h). Current densities after 5 h reaction were improving about 20% when the sample temperature was high (e.g., 37 and 55°C). The detection range increased along with the decrease of external resistance. The acetate concentrations of AD effluents as determined by the biosensor where within 24.2% of the ones determined by gas chromatography. Nevertheless, the application of the biosensor for monitoring acetate in environmental samples could still be promising.

Formation process and mechanism of humic acid-kaolin complex determined by carbamazepine sorption experiments and various characterization methods

To explore the formation process and mechanism of organic matter and organic-mineral complex under humification and mineralization conditions, a series of samples including humic acid, kaolin, and humic acid-kaolin complex were prepared using a subcritical water treatment method (SWT) under specific temperature, pressure and reaction time conditions. HA was used as a surrogate for natural organic matter because it has a similar abundant pore structure, variety of carbon types, and chemical components. These samples were used in carbamazepine (CBZ) sorption experiments and characterized by a variety of techniques. The polymerization of humic acid under the conditions of increased temperature and pressure resulted in an increase in specific surface area and molecular quantity. In addition, the degree of aromaticity rose from 59.52% to 70.90%. These changes were consistent with the transformation from ‘soft carbon’ to ‘hard carbon’ that occurs in nature. The results of sorption experiments confirmed the interaction between humic acid and kaolin from the difference between the predicted and actual Qe values. The conceptual model of humic acid-kaolin complex could be deduced and described as follows. Firstly, the aromatic components of humic acid preferentially combine with kaolin through the intercalation effect, which protects them from the treatment effects. Next, the free carboxyl groups and small aliphatic components of humic acid interact on the surface of kaolin, and these soft species transform into dense carbon through cyclization and polymerization. As a result, humic acid-kaolin complex with a mineral core and dense outer carbonaceous patches were formed.