Effect of activated carbon electrode material characteristics on hardness control performance of membrane capacitive deionization.

Capacitive deionization (CDI) is an electrochemical-based water treatment technology that has attracted attention as an effective hardness-control process. However, few systematic studies have reported the criteria for the selection of suitable electrode materials for membrane capacitive deionization (MCDI) to control hardness. In this study, the effect of electrode material characteristics on the MCDI performance for hardness control was quantitatively analyzed. The results showed that the deionization capacity and the deionization rate were affected by the specific capacitance and BET-specific surface area of the activated carbon electrode. In addition, the deionization rate also showed significant relationship with the BET specific surface area. Furthermore, it was observed that the deionization capacity and the deionization rate have a highly significant relationship with the BET specific surface area divided by the wettability performance expressed as the minimum wetting rate (MWR). These findings highlighted that the electrode material should have a large surface area and good wettability to increase the deionization capacity and the deionization rate of MCDI for hardness control. The results of this study are expected to provide effective criteria for selecting MCDI electrode materials aiming hardness control.

Simultaneous removal of heavy metals and dyes in water using a MgO-coated Fe3O4 nanocomposite: Role of micro-mixing effect induced by bubble generation.

This study focused on the development of a nano-adsorbent for contaminant removal without the use of any external energy. An eco-friendly Fe3O4@MgO core-shell nanocomposite was synthesized and tested for the removal of a heavy metal, lead (Pb2+) and a dye, rhodamine B (RhB). The addition of H2O2 into the system enabled the self-mixing of the aqueous solution containing Fe3O4@MgO through the generation of bubbles. This system showed an excellent removal efficiency of 99% in just 15 min for Pb2+ and 120 min for RhB, which is far better than the control experiment (without H2O2). The cation exchange mechanism dominated in the removal of heavy metals, while the adsorptive removal of dye proceeded through the H-bonding between Mg(OH)2 and dye molecules. The removal efficiency increased exponentially with the increase of H2O2 at the optimal concentration of 5% and it was effective over a wide pH range. Moreover, the performance of the Fe3O4@MgO-H2O2 system was verified for other heavy metals such as Cd, Ni, Zn, Co, and Cu, demonstrating that the Fe3O4@MgO-H2O2 system can be widely implemented in the treatment of real water matrices contaminated with heavy metals and organic dyes.

Carbon-nitride-based micromotor driven by chromate-hydrogen peroxide redox system: Application for removal of sulfamethaxazole.

In this study, a Janus Fe/C3N4 micromotor driven by a chromate-hydrogen peroxide (Cr(VI)/H2O2) redox system was developed and its movement was analyzed. The motion of the micromotor was tracked via nanoparticle tracking analysis (NTA) and the corresponding diffusion coefficients (D) were determined. The NTA results revealed that D = 0 in water in the absence of additives (Cr(VI) or H2O2). The addition of H2O2 resulted in an increase in D from 0 to 12 × 106 nm2 s-1, which further increased to 20 × 106, 26.5 × 106, 29 × 106, and 44 × 106 nm2 s-1 with the addition of 0.5, 1, 2, and 5 ppm of Cr(VI), respectively. Cr(VI) alone did not efficiently propel the Fe/C3N4-based micromotor. Therefore, it was proposed that the Cr(VI)/H2O2 redox system generates O2, which plays a major role in the movement of the C3N4-based micromotor. In addition, the formation of reactive species, such as OH and 1O2, was confirmed through electron spin resonance experiments. The reactive species efficiently degraded sulfamethaxazole (SMX), an organic pollutant, as demonstrated through degradation studies and product analyses. The effects of various parameters, such as H2O2 concentration, Cr(VI) concentration, and initial pH on the movement of micromotor and degradation of SMX were also documented.

Factors associated with partitioning behavior of persistent organic pollutants in a feto-maternal system: A multiple linear regression approach.

Prenatal exposure to persistent organic pollutants (POPs) has been a matter of particular concern because such exposure can severely affect the health of the fetus. The mechanistic understanding of the partitioning behavior of POPs in the feto-maternal system and the associated factors, however, have rarely been studied. Here, we employed a new approach based on multiple linear regression (MLR) analysis to predict the feto-maternal ratio (FM-ratio) of POPs and to assess the factors associated with feto-maternal partitioning behavior. Two preliminary exploratory MLR models were built using physiological conditions of the participants, and molecular descriptors were calculated with a computational model. The FM-ratio was calculated from the concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), and polybrominated diphenyl ethers (PBDEs) in 20 pairs of maternal and cord blood. The models showed that the lipids and cholesterols in the maternal and cord blood and the placenta significantly influence the partitioning of POPs. The body mass index (BMI) change during pregnancy was also related to the FM-ratio. The physicochemical properties associated with lipophilicity and molecular size were also related to the FM-ratio. Even though the results should be interpreted with caution, the preliminary MLR models illustrate that feto-maternal partitioning is governed by transplacental transporting mechanisms, toxicokinetics, and the molecular physicochemical properties of POPs. Overall, the new approach used in this study can improve our understanding of the partitioning behavior in the feto-maternal system.

In situ chemical oxidation of contaminated groundwater using a sulfidized nanoscale zerovalent iron-persulfate system: Insights from a box-type study.

We report the potential of a sulfidized nanoscale zerovalent iron-persulfate (S-nZVI-PS) system for in situ chemical oxidation (ISCO) of groundwater pollutants. The study was conducted using a sand-filled rectangular box with a permeable reactive barrier of S-nZVI as a facsimile of the ISCO system. Synthetic water contaminated with a target pollutant (reactive black-5, RB-5) was continuously passed through the box. The injection of PS led to the complete removal of RB-5 and the system remained reactive for approximately 12 days. This system has a benefit that the oxidation products of S-nZVI (i.e., Fe3O4, Fe2O3, and FeSO4) can further activate PS to retain its reactivity. In a separate trial, this method exploited oxidation, reduction, adsorption and co-precipitation mechanisms that conspired to remove two different groundwater pollutants- arsenite and 1,4-dioxane. These results confirmed the utility of S-nZVI-PS as a mediator of ISCO processes to degrade groundwater pollutants.

Effects of upper-extremity movements on electromyographic activities of selected trunk muscles during leaning forward.

BACKGROUND: Leaning forward has been accepted as a foundational approach to facilitate trunk-stabilizing muscles in the abdominal and lumbopelvic regions for patients with back pain during rehabilitation. However, how trunk muscles are activated and recruited during leaning forward performed under dynamic upper-extremity motion conditions is not completely understood. OBJECTIVE: To determine whether activation of selected trunk muscles changes depending on shoulder movements during leaning forward exercise in healthy young adults. METHODS: Twenty-four healthy adults (6 men and 18 women) participated in this study. The participants performed 3 types of leaning forward exercises: leaning forward alone (leaning forward 1), leaning forward with horizontal shoulder abduction (leaning forward 2), and leaning forward with shoulder flexion (leaning forward 3). Surface electromyography (EMG) was used to record activation of the erector spinae (ES), multifidus (MF), rectus abdominis (RA), and internal oblique (IO) on the dominant side. RESULTS: There was a significant main effect of exercise type on the activation of the IO, RA, and MF muscles. Activation of the IO and MF during leaning forward 1 was significantly decreased compared to activation in leaning forward 2 and 3; the activation of IO and RA showed the greatest increase during leaning forward 3. Furthermore, the IO/RA ratio was significantly increased during leaning forward 2 and 3 in comparison to leaning forward 1; the MF/ES ratio was also significantly increased during leaning forward 3, compared with leaning forward 1. CONCLUSION: The integration of shoulder movements during leaning forward exercises could be effective in the facilitation of EMG activity of IO and MF muscles, especially with shoulder flexion.