Study On Degradation Of Organic Pollutants In Water By Diaphragm Gas-Liquid Discharge Plasma

Low-temperature plasma water treatment technology is a new type of advanced oxidation processes which integrates the mothods of physics,chemistry and optics.It can form multi-factor synergistic effect such as ultraviolet irradiation,high energy electron bombardment and high oxidizing active particle.It has the characteristics of fist reaction rate,strong oxidation ability,no secondary pollution and so on.It has obvious advantages in the treatment of refractory organic wastewater.Among them,the gas-liquid two-phase discharge plasma technolbgy has the advantages of easy discharge and fast mass transfer,and it has become a hotspot in organic wastewater treatment.In this paper,a diaphragm gas-liquid discharge reactor was designed and the discharge characteristics of the reator in different discharge gas were studied.The experiment was carried out under different experimental conditions using the azo dye brilliant red B and phenol as the model pollutants.The experimental results are summarized below:?1?Strong oxidizing radicals such as OH and O· are produced during the diaphragm gas-liquid discharge,and the relative spectral intensity is highest when oxygen is used as the discharge carrier gas;in the case of air and argon as the discharge gas,the emission peaks are mainly N₂ and Ar I bands;with the increase of the discharge time,the O₃ and H₂O₂ in the liquid phase are gradually increased under different discharge gas;the highest concentration of O₃ and H₂O₂ are produced in the case of oxygen,and its concentration are 11.42 mg/L and 85.38 mg/L after 10 min of discharge.?2?When the input energy is constant,the degradation efficiency of brilliant red B increases slightly with the increase of the number of the discharge holes;high acidity and low conductivity are favorable for the removal of brilliant red B and phenol;in the diaphragm gas-liquid discharge system,the removal efficiency is the best when oxygen was used as the discharge gas,followed by argon and air;the energy efficiency of phenol removal is up to 2.250 g/kWh in the case of oxygen.?3?Addition of hydroxyl radical scavenger inhibited the degradation of brilliant red B and phenol,which indicates that ·OH radical is an important active substance in the process of decomposition of organic pollutants;the addition of Fe²⁺ catalyzed the degradation of brilliant red B and phenol,and the opt:imum concentration of Fe²⁺ in the discharge system is 0.4 mmol/L.?4?Cl-,NO₃^-,NO₂^-,SO₄^2-,CH₃COOH,HCOOH,and HOOCCOOH were detected in the degradation of brilliant red B,indicating that the azo bond of the red B dye and the ring structure of benzene ring and naphthalene ring are opened and broken;there are four main intermediates produced during phenol degradation:resorcinol,hydroquinone,p-benzoquinone and catechol,where the concentration of intermediate product increases first and then decreases,and they gradually disappear with prolonging the discharge time,and the final products are carbon dioxide and water;.