Review on electrical discharge plasma technology for wastewater remediation

The use of vanillin as a building block for the chemical industry is discussed in this article. Vanillin is currently one of the only molecular phenolic compounds manufactured on an industrial scale from biomass. It has thus the potential to become a key-intermediate for the synthesis of bio-based polymers, for which aromatic monomers are needed to reach good thermo-mechanical properties. After a first part dedicated to the current sourcing of vanillin, this article focuses on the alkaline oxidation lignin-to-vanillin process, reporting advantages and limits, discusses the various postdepolymerization methods for product isolation and finally examines the outlook for the wider use of vanillin as a key building block for the chemical industry.

Vanillin Production from Lignin and Its Use as a Renewable Chemical

Advanced oxidation processes for the removal of natural organic matter from drinking water sources: A comprehensive review.

Degradation of pharmaceutical compounds in water by non-thermal plasma treatment.

Monitoring changes in the structure and properties of humic substances following ozonation using UV-Vis, FTIR and (1)H NMR techniques.

Oxidation of aromatic compounds of phenolic (paracetamol, β-oestradiol and salicylic acid) and carboxylic (indomethacin and ibuprofen) structure used in pharmaceutics was studied. Aqueous solutions were treated with pulsed corona discharge (PCD) as a means for advanced oxidation. Pulse repetition frequency, delivered energy dose and oxidation media were the main parameters studied for their influence on the process energy efficiency. The PCD treatment appeared to be effective in oxidation of the target compounds: complete degradation of pollutant together with partial mineralization was achieved at moderate energy consumption; oxidation proceeds faster in alkaline media. Low-molecular carboxylic acids were identified as ultimate oxidation by-products formed in the reaction.

Oxidation of aqueous pharmaceuticals by pulsed corona discharge

https://www.researchgate.net/profile/Sergei_Preis/publication/258054814_Pulsed_corona_discharge_the_role_of_ozone_and_hydroxyl_radical_in_aqueous_pollutants_oxidation/links/53dd3b4a0cf2cfac99291426.pdf

Pulsed corona discharge: the role of ozone and hydroxyl radical in aqueous pollutants oxidation.

The accumulation of nitrogen-containing ions formed in aqueous solutions dispersed in air and treated with pulsed corona, dielectric barrier and spark electric discharges, was studied dependent on electric conductivity and pH of treated solutions. The impact of conductivity to the spark and corona discharge is determined by the increased ohmic losses in the reactor. In contrast, the character of dielectric barrier discharge is significantly changed with growing conductivity resulted in increased nitrite-to-nitrate ratio. In alkaline solutions the production of nitrites is increased for the spark and the barrier discharge; the corona discharge produce only nitrates. The amount of nitrates produced in pulsed corona discharge at energy doses characteristic for potable water treatment is about 100 times lower than their maximum permissible concentration.

Formation of Nitrite- and Nitrate-Ions in Aqueous Solutions Treated with Pulsed Electric Discharges

The research into oxidation of aqueous humic substances (HS) with pulsed corona discharge (PCD) was undertaken to estimate the energy efficiency of the treatment. The PCD system consists of a voltage pulse generator and reactor, in which the gas-phase discharge generating OH radicals and ozone treats the water showered between electrodes. The influence of HS initial concentration, pulse repetition frequency, water flow rate, and the atmosphere composition was evaluated by the decrease in total organic carbon (TOC) and color. The PCD treatment reduced TOC by 40 to 50% and the color by up to 97%. The PCD energy efficiency ranged about 20 g kW−1 h−1 in air and 30 g kW−1 h−1 in oxygen for the lowest initial color of about 50 Pt-Co degrees. Ozone contributed about 30% to the color reduction and only 15% to the reduction in TOC, indicating predominant role of OH radicals in mineralization of oxidation by-products.

Pulsed corona discharge for degradation of aqueous humic substances

Water treatment by gas-phase pulsed corona discharge (PCD) relies mainly on utilization of ozone and OH radicals as oxidizing agents. In a configuration where the treated solution is showered through the plasma zone, the gas–liquid contact surface is the primary OH-radical formation site and the interface in the mass transfer of ozone. Its significance to overall process efficiency is therefore notable. In this study, the effect of varying contact surface area at different discharge powers was investigated from the perspective of efficient utilization of the two prime oxidants in slow reaction with oxalate. It is seen that increasing the area of the contact surface improves OH-radical utilization up to the point where the pollutant oxidation efficiency abruptly decreases presumably because of unfavorable pulse energy distribution in the gas–liquid mixture. The existence of an optimal area for a given power has implications for future studies in the design of pulsed plasma applications for water treatment.

Iakov Kornev

Papers

Oxidation of aqueous pharmaceuticals by pulsed corona discharge

Pulsed corona discharge: the role of ozone and hydroxyl radical in aqueous pollutants oxidation.

Formation of Nitrite- and Nitrate-Ions in Aqueous Solutions Treated with Pulsed Electric Discharges

Pulsed corona discharge for degradation of aqueous humic substances

Pulsed Corona Discharge in Water Treatment: The Effect of Hydrodynamic Conditions on Oxidation Energy Efficiency