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Non-thermal plasma in ultrafine water mist (UWM) is proposed to increase the content of COOH groups on the surface of raw walnut shell in order to improve its performance in the removal of Cu(II) from wastewater.The modified walnut shell surface was characterized by various techniques (BET, SEM-EDX and XPS), and it was observed that more COOH groups were generated. Oxygen disassociated from water mist by plasma bonded with the walnut shell to form activated sites of COOH groups. After Cu(II) adsorption, the COOH group content in the walnut shell decreased because some groups were changed into C-O groups by Cu(II) chemisorption with COOH groups. The Cu(II) removal efficiency was 33.5% for raw walnut shell; however, the efficiency increased to 98% after plasma modification for 15 min under 3 g min À1 watermist. The maximum Cu(II) adsorption capacity of the UWM-plasma-modified WNS was 39.4 mg g À1 at pH 5.3 and 25 C, around 8 times that of the raw WNS. This implies that UWM-plasma modification is a potential method for improving the Cu(II) adsorption performance of raw biomass.

To explore the influence of different processing parameters on the efficiency of electrochemical machining and the surface morphology, the influence of different processing parameters on the removal of spikes was simulated by COMSOL Multiphysics simulation software. And combined with experiments, the influence of different processing parameters on electrochemical machining micro-surface was analyzed and compared. The results showed that the removal amount increased with the increase of machining voltage, machining time, and electrolyte concentration, and decreased with the increase in the machining gap. The appropriate processing parameters not only reduce the surface roughness from 2.56μm to 0.57μm, but also change the difference between the surface micro high point and the micro low point from 280μm to 170μm, and the finishing effect is greatly improved.

During the plasma modification process on activated carbon surface, reactive gas of O2 in the plasma field dominates the formation of oxygen-containing groups on activated carbon surface, which is a key factor that affects the mercury adsorption. Previous studies showed that change the O2 concentration would influence the generation of oxygen-containing groups and thus affect the mercury adsorption. It is important to investigate the effects of O2 concentration in the non-thermal plasma field on the mercury adsorption characteristic of modified activated carbon. This work presents the results of the novel use of non-thermal plasma in Ar-O2 gas to increase surface oxygen functionality on the surface of a commercially available biomass carbon. The volume fraction of O2 in the Ar-O2 mixture was varied from 10 % to 100 %. The surface physical and chemistry properties of modified activated carbon were analyzed by using BET, FT-IR and XPS techniques. Results showed that activated carbon modified by Ar-O2 non-thermal plasma showed significantly better mercury removal performance compared with the original activated carbon. Moreover, increase O2 concentration in the plasma field can further increase the mercury removal efficiency of modified activated carbon. Higher O2 concentration can produce more O radicals during plasma system and facilitated the formation of carbonyl and ester groups on activated carbon surface and thus enhanced the mercury removal. Temperature programmed desorption (TPD) results indicated that mercury reacted with ester groups were prior to carbonyl groups. When O2 concentration increased to 100 %, the ester groups of modified activated carbon dominated the mercury adsorption process.