Needle electrode design of pulsed high voltage discharge reactor for performance enhancement of 4-chlorophenol degradation in highly conductive solution

Abstract In this paper, a pulsed high voltage discharge (PHVD) reactor composed of a new type of high-voltage (HV) needle electrode and mesh grounding electrode was utilized to degrade 4-chlorophenol (4-CP). The effect of needle installation position on 4-CP degradation efficiency in solution systems with different conductivities was studied. It is verified that the recessed- and flush-tip structures could effectively overcome the main technical problem of protruded-tip HV electrode, which is that how to maintain stable discharge in the solution with high conductivity. When the conductivity of solution surpassed 116 μS cm-1, the recessed-tip and flush-tip electrodes possessed higher energy efficiency than that of the protruded-tip electrode. Within 40 min, the flush-tip electrode had the highest 4-CP removal rate (86.2%) in pure water, which could further increased to 95.8% via increasing immersion depth of net electrode. Comprehensively considering the experimental results of 4-CP removal rate, discharge characteristic and tail gas emission, it is indicated that the optimal installation positions were 0-F and 5-R. Meanwhile, the increase in immersion depth could reduce the generation of tail gas (e.g. O3 and NOX) obviously. The possible mechanism of 4-CP degradation via PHVD was proposed.