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A rapid and simple method for the extraction and preconcentration of ceftazidime in aqueous samples has been developed using dispersive liquid-liquid microextraction followed by high-performance liquid chromatography analysis. The extraction parameters, such as the volume of extraction solvent and disperser solvent, salt effect, sample volume, centrifuge rate, centrifuge time, extraction time, and temperature in the dispersive liquid-liquid microextraction process, were studied and optimized with the experimental design methods. Firstly, for the preliminary screening of the parameters the taguchi design was used and then, the fractional factorial design was used for significant factors optimization. At the optimum conditions, the calibration curves for ceftazidime indicated good linearity over the range of 0.001-10 μg/mL with correlation coefficients higher than the 0.98, and the limits of detection were 0.13 and 0.17 ng/mL, for water and urine samples, respectively. The proposed method successfully employed to determine ceftazidime in water and urine samples and good agreement between the experimental data and predictive values has been achieved.

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This research has analysed the physiochemical properties of a catalyst that has been developed - biochar-La, including BJH, BET, EDX, SEM, FTIR, pHpzc, and iodine number. The catalyst consisted of effective functional groups, including C=S, C-O, C=C, -COOH and O-H, with a specific surface area of 31.2 m/g. The catalyst was used in the biochar-La/ultrasonic/persulphate system to remove phenol from wastewater. The kinetics, mechanism, and reusability of the catalyst for the phenol removal from synthetic wastewater were determined. The results suggested that phenol removal kinetics follows pseudo-first-order model (k = 0.0386 1/min), and the catalyst can be reused three times. The potential of operation of the biochar-La/ultrasonic/persulphate system - with the effective removal of phenol and other organic compounds from real petrochemical wastewater - was tested. The results indicated that the removal of phenol from the petrochemical wastewater with a relatively high total dissolved solid is >99%. The gas chromatography-mass spectrometry (GC-mass) test revealed that the complete decomposition of some contaminants in the petrochemical wastewater had occurred, as HO and CO were detected. The contribution of a heterogeneous mechanism for phenol oxidation by biochar-La/ultrasonic/persulphate was calculated to be 60%. Overall, the results showed that the biochar-La/ultrasonic/persulphate system is very effective and promising for the removal of phenol from the petrochemical wastewater.

In this paper, the effects of phenol concentration, pH, catalyst dose, persulfate concentration, temperature and contact time on the phenol removal from wastewater by activation of persulfate (S 2 O 8 −2 ) in the presence of biochar modified by lanthanum chloride and ultrasonic waves (US) are optimized. Experimental design and optimization were carried out by response surface methodology. The optimum conditions for the maximum phenol removal were obtained pH of 4, phenol concentration of 86 mg/L, catalyst dose of 43 mg/L, persulfate concentration of 86 mg/L, temperature of 41 °C and contact time of 63 min. The optimum phenol removal from synthetic wastewater was attained 97.68%. Phenol removal by the mentioned system was fitted with the first-order kinetic model. The combination of the ingredients of 'S 2 O 8 −2 /US/Biochar-LaCl 3 ' system had a synergistic effect on the phenol removal.