Wen-Chun Wang's research while affiliated with Dalian University of Technology and other places

A porous functionalized resin was produced using nanosecond pulsed discharge for the purpose of removing Ni(II). The implications of discharge time, O 2 concentration, and solution pH on adsorption capacity were explored. Studies indicated that nanosecond pulsed discharge‐modified resins in 5 min of discharge time and 8% of O 2 concentration had a removal efficiency of 97.2%, and an increase of 36% compared to the raw. Furthermore, the residual Ni(II) concentration (0.3 mg/L) is well below the national permitted emission standard (0.5 mg/L). The rise in Ni(II) removal efficiency is associated with the increased specific surface area and oxygen‐containing functional groups. Chemisorption played an important role in the removal of Ni(II) by raw and modified resins.

In this paper, a high‐efficiency adsorbent resin is prepared by nanosecond pulsed discharge plasma to remove Cu(II), Pb(II), and Cd(II). The effects of discharge parameters, pH, and adsorbent dose on adsorption capacity of resins are evaluated. Correspondingly, the pore structure and chemical groups are analyzed using scanning electron microscopy, N2 adsorption–desorption, and X‐ray photoelectron spectroscopy. The equilibrium adsorption capacity of modified resins for Cu(II), Pb(II), and Cd(II) can reach up to 6.84, 10.87, and 9.22 mg/g, respectively, which is increased by 62%, 49%, and 48% compared with that of the raw. The improvement of adsorption capacity is attributed to the enhancement of specific surface area and mesopores number, as well as the generation of plentiful amino and O‐containing functional groups. D301 resins are treated by nanosecond pulsed discharge plasma to improve its removal capacity for heavy metal ions. After modification, a large number of amino and O‐containing functional groups are implanted and the specific surface area of the resin increases, which leads to an increase in the adsorption capacity of the resin for heavy metal ions.

In this paper, shielding gas (He) and shielding quartz tube (straight tube and conical tube) is added to nanosecond pulsed He gas-liquid discharge for the purposes of enhancing the plasma volume and productions of •OH and H2O2. The plasma properties, including current-voltage waveforms, the temporal-resolved discharge images, optical emission spectra, gas temperature, electron density, and the •OH and H2O2 productions are analyzed and compared among different discharges generated under the cases of no shielding, shielding He gas, shielding straight tube, and shielding conical tube. The results show that adding shielding gas and tubes in the discharge reactor can decrease the gas temperature and electron density, but enhance the plasma volume and area of plasma-liquid interface in comparison with no shielding case. In comparison, the addition of shielding gas has the most benefit for enhancing the concentrations of •OH and H2O2 produced by gas-liquid discharge. Adding a shielding conical tube slows down the decrease extent of •OH and H2O2 productions caused by increasing discharge gap. When the discharge gasp excesses 6 mm, adding a shielding conical quartz also has an obvious enhanced effect on the production of •OH and H2O2 in compared with no shielding case. While adding a shielding straight tube with small diameter has a little effect on H2O2 production, even a negative effect on •OH production.

In this study, comparisons of spatiotemporal resolved images, optical emission spectroscopy technology, and electrical characteristics diagnosis were used to investigate the conversion and optimization of the discharge modes in a packed bed reactor (PBR) in which dielectric materials with different dielectric constants were employed under different peak voltages. The effects of the peak voltages and dielectric materials on the production of reactive species, such as N 2 ( C 3 Π u ) and N 2 + ( B 2 Σ u + ) , were also studied for plasma applications. The results show that, when a polytetrafluoroethylene (PTFE) column is employed, with an increase in the peak voltages, the form and modes of the discharge both change. First, the discharge channel becomes ‘wider’ and the discharge volume becomes larger, which results in more reactive species. Second, the discharge mode changes from surface discharge to diffuse discharge during the falling edge of the voltage pulse. When the dielectric constant of the dielectric material is increased, the intensity of the surface streamer decreases during its shorter propagation path because of more electron collision losses. Moreover, a different discharge mode, called ‘local discharge’, was observed at the contact point. Under the same experimental conditions, the numbers of nitrogen molecules distributed at different vibrational levels and the reactive species produced in the alumina PBR were fewer than those in the PTFE PBR.

In this work, high-voltage pulsed Ar gas–liquid discharge synergizing iron-based catalyst-activated persulfate (PS) was employed to degrade methylene blue (MB) in water. The catalytic performances of two types of iron-based catalysts, namely the homogeneous catalyst Fe ²⁺ and the heterogeneous catalyst nano-Fe 3 O 4 , were compared. Correspondingly, the plasma gas temperature and excited species were calculated and diagnosed using optical emission spectra. It was found that the introduced plasma process significantly enhanced the degradation efficiency of MB by the PS/Fe ²⁺ and the PS/Fe 3 O 4 systems. After 20 min of treatment, the MB degradation efficiency reaches 97.5% and 83.1% in the hybrid plasma/PS/Fe ²⁺ and plasma/PS/Fe 3 O 4 systems, respectively, which is 37.9% and 35.6% higher than that in the PS/Fe ²⁺ and PS/Fe 3 O 4 systems. The synergistic mechanism and key reactive species responsible for MB degradation in hybrid plasma/PS/Fe ²⁺ and plasma/PS/Fe 3 O 4 were explored using the addition of radical scavengers and control experiments under various conditions. The homogeneous catalyst Fe ²⁺ exhibits better activation performance in PS and plasma than that of the heterogeneous catalyst nano-Fe 3 O 4 .

Atmospheric pressure electrolyte cathode discharge plasma presents a great potential on detecting heavy metal pollutants. In this paper, a novel microsecond pulsed electrolyte cathode discharge was generated and coupled with temporal resolved atomic emission spectra to analyze Cu element, as one of the representative heavy metals. The waveforms of voltage and current, as well as optical emission spectra of discharge were investigated, and the experimental conditions were optimized. The spatiotemporal resolved spectra of Cu I (324.8 nm), OH (A²Σ–X²Π) and N2 (C³Πu–B³Πg) were diagnosed. The spatiotemporal distributions of gas temperature and electron density were calculated by the rotational temperature of OH (A) and the Stark broadening of Hβ (486.1 nm), respectively. It was found that the optimal detection sensitivity of Cu are obtained under the conditions of HNO3 solution with 1.0 pH value, 3.0 mL/min solution flow rate, 8.5 kV pulse peak voltage, and 100 μs pulse width. The interferences of spectral line of Cu I (324.8 nm) are mainly sourced by the spectral bands of N2 (C − B) and OH (A − X), which could be reduced by the temporal resolved spectra. The limit of detection of Cu was improved from 0.217 mg/L to 0.092 mg/L by acquiring spectra only in 25–100 μs, under the optimal conditions. Furthermore, the gas temperature and electron density play important roles in the spatiotemporal evolution of discharge and the improvement of detection sensitivity for elemental analysis.

The persulfate activation by nanosecond pulsed gas-liquid discharge (NPG-LD) is employed to degrade the trimethoprim (TMP) in water. The results show that persulfate addition enhances the degradation of TMP by NPG-LD through an obvious synergetic effect. With treatment time of 50 min, the high removal efficiency and energy yield reach 94.6% and 0.57 gkWh⁻¹ in air NPG-LD with the addition of persulfate, respectively, which is 13.5% and 0.09 gkWh⁻¹ higher than that in solo air NPG-LD, respectively. Correspondingly, the calculated synergetic factor achieves 1.62, indicating the synergetic effect is established. The activation mechanism of persulfate by NPG-LD is analyzed by the measurement of reactive species and the effects of radical scavenger addition on TMP removal. It is found that the synergetic effect between NPG-LD and persulfate is attributed to the increased production of OH, H2O2, and . Besides, the TMP degradation by NPG-LD and persulfate synergetic system is influenced by discharge working gas, pulse voltage, addition dosage of persulfate, initial TMP concentration, and initial pH value. Subsequently, the degradation pathway of TMP is analyzed using LC-MS/MS.

In this study, a nanosecond‐pulsed discharge plasma is employed to modify the macroporous XAD‐2 resin to improve the adsorption performance of polycyclic aromatic hydrocarbons. After modification, XAD‐2‐20 resin shows great advantage on naphthalene (Nap) adsorption, whose adsorption capacity increased by 80.6% and 43.5% compared with the raw and XAD‐2‐30, respectively. The physiochemical properties of XAD‐2 resin are characterized by scanning electron microscope, N2 adsorption/desorption, X‐ray photoelectron spectroscopy, and Fourier‐transform infrared (FTIR) spectrum. The amount of micro‐mesoporous with a size of 2–3.5 nm are formed and many carbonyl groups (C═O) and ester or carboxylic groups (O–C═O) are introduced on the XAD‐2‐20 surface, and the value of O/C is increased from 14% to 53% compared with the raw resin. XAD‐2 resin is modified by nanosecond‐pulsed discharge plasma in a packed bed to improve the adsorption capacity of polycyclic aromatic hydrocarbons. After modification, the surface structure of XAD‐2 resin becomes rough and a large number of oxygen‐containing functional groups are inserted on the surface, which enhances the adsorption capacity of XAD‐2 resin.

In this paper, a capacitor assisted AC high-voltage was employed to generate a gas–liquid discharge in pure oxygen at atmospheric pressure. The discharge images, waveforms of voltage and discharge current, and optical emission spectra of plasma were diagnosed for the purpose of investigating the discharge modes. The gas temperature (Tg), excitation temperature of hydrogen (Texc), and electron density (ne) were calculated by the spectra of OH (A²Σ–X²Π), the intensity ratio of Hα and Hβ, and the Stark broadening of Hβ, respectively. The effects of applied voltage and capacitance value on the mode transition of discharge were also discussed. It is found that due to the presence of capacitor, not only is the unlimited growth of discharge current restrained, but the transition of discharge mode is also controllable. There are three discharge modes of gas–liquid discharge oxygen plasma (GLDOP), and with the increase of applied voltage or capacitance value, discharge modes are transited from the streamer mode, to the glow-like mode, and to the abnormal glow/arc mode. With the mode transition, the Tg and Texc of GLDOP increase and the ne decreases. In contrast, the change of Tg and ne is negligible when GLDOP maintains one kind of discharge mode.

Humic acid (HA) removal research focuses on the global water treatment industry. In this work, efficient HA degradation with an ultra-high synergetic intensity is achieved by combined bubble discharge with activated carbon (AC). Adding AC to the discharge greatly improves HA removal efficiency and degradation speed; the synergetic intensity reaches 651.52% in the combined system, and the adsorption residual on AC is 4.52%. After 90 min of treatment, the HA removal efficiency reaches 98.90%, 31.29%, and 7.61% in the plasma-AC combined, solo bubble discharge, and solo AC adsorption systems, respectively. During the plasma process, the number of pore structures and active sites and the amount of oxygen-containing functional groups on the AC surface increase, resulting in a higher adsorption capacity to reactive species (H2O2 and O3) and HA and promoting interactions on the AC surface. For HA mineralization, the presence of AC greatly promotes the destruction of aromatic structures and chromophoric HA functional groups.