M.D. Murcia

Enhancement of 4-Chlorophenol Photodegradation with KrCl Excimer UV Lamp by Adding Hydrogen Peroxide

4-Chlorophenol removal combining KrCl excimer UV lamp and H2O2 has been studied, using 4-chlorophenol concentrations of 100 and 250 mg L−1 and molar ratios H2O2: 4-chlorophenol = 1:1, 10:1, 25:1, and 50:1. A ratio of 25:1 achieves the total removal for both 4-chlorophenol and the photoproducts. Comparing these results with those corresponding to the use of excilamp treatment in the absence of H2O2, there is no difference in 4-chlorophenol degradation. The excilamp alone, however, leads to the incomplete removal of photoproducts. Additionally, significant COD decrease is attained in the samples treated with UV/H2O2 and toxicity bioassays with Pseudomonas putida show important toxicity alleviation.

Removal efficiency and toxicity reduction of 4-chlorophenol with physical, chemical and biochemical methods

Chlorophenols are well-known priority pollutants and many different treatments have been assessed to facilitate their removal from industrial wastewater. However, an absolute and optimum solution still has to be practically implemented in an industrial setting. In this work, a series of physical, chemical and biochemical treatments have been systematically tested for the removal of 4-chlorophenol, and their results have been compared in order to determine the most effective treatment based on removal efficiency and residual by-product formation. Chemical treatments based on advanced oxidation processes (AOP) produced the best results on rate and extent of pollutant removal. The non-chemical technologies showed advantages in terms of complete (in the case of adsorption) or easy (enzymatic treatments) removal of toxic treatment by-products. The AOP methods led to the production of different photoproducts depending on the chosen treatment. Toxic products remained in most cases following treatment, though the toxicity level is significantly reduced with combination treatments. Among the treatments, a photochemical method combining UV, produced with a KrCl excilamp, and hydrogen peroxide achieved total removal of chlorophenol and all by-products and is considered the best treatment for chlorophenol removal.

Testing a Pseudomonas putida strain for 4-chlorophenol degradation in the presence of glucose

Abstract One of the most studied process for the decomposition of phenolic compounds involves the use of different microbial species or consortia. The main drawback of biological methods is the possible inhibitory effect of high concentrations of phenolic compounds impacting on the microorganisms. To overcome these difficulty bacteria can be acclimated to higher concentrations of phenols and the use of supplemental carbon sources. In this work a Pseudomonas putida strain isolated from a waste treatment plant receiving phenolic waste was tested for 4-chlorophenol removal using 1% (w/v) glucose as a co-substrate. Total removal of 4-chlorophenol concentrations of 50, 150 and 200 mg l−1 were obtained in approximately 27, 53 and 93 h respectively. For a higher 4-chlorophenol concentration of 250 mg l−1, only 22% of degradation was obtained suggesting that at this high concentration, the 4-chlorophenol exerts an inhibitory effect on the bacteria.

A New Kinetic Model for 4-Chlorophenol Adsorption on Expanded Clay

The adsorption of 4-chlorophenol on an expanded commercial clay used in water purification has been studied. Experiments using 4-chlorophenol concentrations of 50, 100, 250, 500, 750, 1000, 1250 and 1500 mg L-1 were carried out in column reactors at 25ºC.A new adsorption kinetics equation has been developed based on the equation for the variation in solute concentration in the liquid phase, representing the difference between the adsorption rate minus the desorption rate that at equilibrium represents the Langmuir isotherm. This was used to derive a new finite equation for the development of the adsorption curve.

Removal of 4-chlorophenol in a continuous membrane bioreactor using different commercial peroxidases

Abstract Three commercial plant peroxidases, the commonly used soybean (SBP) and horseradish (HRP) and a cheap alternative, artichoke (AKPC), have been tested for the removal of 4-chlorophenol in a continuous tank reactor associated to an ultrafiltration membrane module. An important conversion fall over time was observed both in the reactor and permeate samples with AKPC. For the other peroxidases, this conversion decrease occurred in the reactor only, as a result of the enzyme retention on the membrane, and was rather insignificant in the case of SBP. Supplementary addition of enzyme in the feed stream allowed maintaining high conversions in the case of HRP. Consequently, SBP and HRP were selected as the most appropriate peroxidases. Using them, it was observed that conversion values increased when higher substrate concentrations were used and that the influence of the molar ratio H2O2:chlorophenol and the spatial time was negligible. In all cases, higher 4-chlorophenol conversions were attained with SB...