Sonochemical degradation of the antibiotic cephalexin in aqueous solution

Abstract

The degradation of cephalexin in aqueous solution under ultrasound irradiation was investigated. Biodegradability of the solution was evaluated by the BOD 5 /COD ratio, which was raised from zero to 0.36 after ultrasound treatment, indicating that the ultrasound irradiation process is a successful pre-treatment step to improve the biodegradability of cephalexin solution. The influences of ultrasound power and pH value on the degradation of cephalexin were studied. It was found that the optimal ultrasound power for cephalexin degradation in the system was 200 W and the rate of cephalexin degradation was maximal in the pH range of 6.5 to 8.5. The degradation kinetics of cephalexin in aqueous solution under various operational conditions was also investigated. It was found that the degradation of cephalexin follows a pseudo-first order kinetics.

Biodegradation of Pharmaceutical Wastes in Treated Sewage Effluents by Bacillus subtilis 1556WTNC

“…The cephalexin was selected as a model to investigate the biodegradation of β-lactam antibiotics as function of β-lactamase, because Lin et al (2009) and Guo et al (2010) reported that the cephalexin is one of the most popular antibiotics that are ubiquitously present in sewage effluents at high concentrations due to its resistance to degradation during sewage treatment processes. The results found that 42 isolates presented high growth in the presence of 1 g L −1 of cephalexin.…”

Photocatalytic activity of NiS, NiO and coupled NiS–NiO for degradation of pharmaceutical pollutant cephalexin under visible light

“…If the e À /h + are not recombined, they have the chance to produce powerful oxidants cOH radicals, which in turn react with the pollutant molecules adsorbed on the surface of the photocatalyst and the oxidation reactions is initiated. 8 If the e À and h + recombine on the catalyst surface or in the bulk of the particles the energy will released as heat and degradation is not forwarded. To improve the degradation efficiency, recombination of e À /h + must be minimized.…”

“…The most commonly used methods for removal of cephalexin are sunlight degradation, 3 Fenton oxidation, 4-6 adsorption 7 and advance oxidation processes. 8 In advance oxidation processes, a suitable photocatalyst is activated by incident light with energy higher or equal to the band gap energy of the photocatalyst, and then electron-hole pairs (e À /h + ) are generated. If the e À /h + are not recombined, they have the chance to produce powerful oxidants cOH radicals, which in turn react with the pollutant molecules adsorbed on the surface of the photocatalyst and the oxidation reactions is initiated.…”

“…At pH higher than 6.9 it is mainly presents as the anionic form and at pH lower than 2.6, cephalexin is in the cationic form and at the pH range of 2.6-6.9 it mainly stands in zwitterion. 8 The isoelectric pH (PI) at which that cephalexin becomes neutral is about 5.5. At pH lower than 2.6 the repulsion force between protonated cephalexin molecules and of catalyst surface limited the adsorption of the pollutant molecules causing lower degradation efficiency.…”

“…Benzoquinone is a super oxide radical quencher and according to eqn (5)- (8), lowered the generation of OH radicals. Therefore isopropanol and benzoquinone acting as organic scavenger and considerably lowered the degradation efficiency of cephalexin.…”