Removal of Phenol by Ozonation in Strongly Alkaline Conditions using a Jet Loop Reactor Operated in Continuous Phase

Industrial wastewater streams frequently contain elevated concentrations of phenolic compounds that present severe ecological hazards due to their inherent toxicity and environmental persistence in natural water bodies. Prior research has shown that advanced oxidation processes can effectively degrade these hazardous aromatic pollutants by generating highly reactive hydroxyl radicals in aqueous environments. Conventional biological treatment methods often fail when facing the high chemical oxygen demand and inhibitory nature of concentrated industrial effluents. Ozonation has emerged as a robust oxidative technology, yet its practical efficiency is strictly governed by reactor geometry and the specific chemical characteristics of the liquid phase being treated. Strongly alkaline environments are recognized for their ability to accelerate the decomposition of molecular ozone into more aggressive oxidative species, thereby improving the degradation of complex organic structures. The integration of specialized reactor designs like the jet loop system offers a promising pathway for enhancing gas-liquid contact and reaction kinetics. This absence of evidence motivated a comprehensive investigation into the performance of continuous-flow jet loop reactors operating under extreme pH conditions to treat these pollutants.

This research rigorously evaluates the operational performance of a continuously operated jet loop reactor for the oxidative degradation of phenol under highly alkaline conditions to improve industrial wastewater quality. The investigators sought to characterize how variations in the inlet ozone gas concentration dictate the steady-state removal efficiencies of organic carbon and chemical oxygen demand. The study systematically examines the influence of hydraulic retention time on the overall effectiveness of the oxidation process within the specialized reactor vessel. Analysis focuses on the complex relationship between the initial influent pollutant load and the resulting quality of the effluent during continuous phase operation. The research team aimed to identify the precise operational parameters required to achieve the total elimination of the target aromatic contaminant from the wastewater stream. This work provides a detailed quantitative assessment of the extent of total organic carbon mineralization achieved during the high-pH ozonation process. Scientists intended to establish a scalable model for industrial wastewater treatment that maximizes pollutant destruction while minimizing the required hydraulic residence time.

The experimental configuration utilized a specialized Jet Loop Reactor (JLR) specifically engineered for continuous phase operation to maximize gas-liquid mass transfer efficiency during the oxidation of organic pollutants. Highly alkaline conditions were strictly maintained throughout the treatment cycle to facilitate the rapid generation of secondary oxidative radicals from the ozone precursor. Ozone gas was introduced into the system at specific concentrations ranging from 17.5 to 56.5 grams per cubic meter to evaluate the oxidative capacity of the reactor. The researchers precisely adjusted the hydraulic retention time (HRT) to determine the optimal duration for contact between the ozone and the phenolic molecules. Effluent samples were systematically collected once the system reached steady-state conditions to measure residual phenol, Chemical Oxygen Demand (COD), and Total Organic Carbon (TOC). Standardized analytical protocols were strictly followed to quantify the degradation of the aromatic ring and the overall degree of mineralization in the treated water. The study employed a continuous flow regime to simulate real-world industrial processing conditions and assess the long-term stability of the oxidative treatment system.

Phenol removal efficiency reached a significant 97.8% when the reactor operated with an initial inlet ozone concentration of 17.5 grams per cubic meter under steady-state conditions. Increasing the ozone dosage to 56.5 grams per cubic meter ensured that the target aromatic compound was no longer detectable in the steady-state effluent. The highest observed removal efficiency occurred at a hydraulic retention time of 8 hours, which allowed for sufficient reaction time between the species. Under these optimized conditions, the system achieved a 76.8% reduction in chemical oxygen demand and a 48.2% reduction in total organic carbon levels. Elevated influent concentrations of the phenolic pollutant were found to inversely impact the removal percentages for all measured chemical parameters in the effluent. Steady-state data indicated that while the primary contaminant was effectively eliminated, the complete mineralization of intermediate oxidation products required more aggressive treatment conditions. The reactor maintained stable performance throughout the continuous operation phase, demonstrating the reliability of the jet loop design for high-alkalinity ozonation.

The jet loop reactor demonstrates exceptional capability as a high-performance platform for the remediation of industrial wastewater containing toxic phenolic substances that are resistant to conventional treatment. Operating the system under strongly alkaline conditions significantly boosts the oxidative potential of ozone, facilitating the breakdown of resilient aromatic structures. Precise optimization of the hydraulic retention time is a fundamental requirement for maximizing the reduction of chemical oxygen demand in continuous-flow reactors. These results indicate that high ozone concentrations can achieve the total elimination of specific hazardous compounds in challenging industrial wastewater environments. Future implementation of this technology should target complex industrial effluents where traditional biological processes are often inhibited by high chemical toxicity. The study provides a robust technical framework for scaling up continuous ozonation processes for large-scale environmental protection and industrial water recycling initiatives. Researchers conclude that the integration of advanced reactor designs with optimized chemical environments is essential for achieving sustainable and efficient wastewater purification.