Preparation of an electrochemical sensor utilizing graphene-like biochar for the detection of tetracycline.

Tetracycline (TC), which is ubiquitous in the aquatic environment, can cause ecological imbalance and adversely affect human health. Therefore, a quick, inexpensive, and easy method for the detection of TC in water systems is highly desirable. This study reports the development of a novel electrochemical sensor from waste peanut shell for the quick detection of TC in water. Raman and TEM lattice mapping analyses confirmed the successful preparation of graphene -like biochar from waste peanut shells (PSs) via hydrothermal and pyrolysis processes. An electrochemical sensor, PS@glassy carbon electrode (PS@GCE), was then developed by coating the prepared graphene-like biochar on the surface of a glass electrode to enhance its conductivity. The feasibility of using this sensor for the detection of TC in the aqueous system was investigated. The PS@GCE sensor exhibited excellent sensitivity with a low detection limit of 3.6 × 10--9 nM and a linear range of 10-10-102 µM. These results were attributed to the large specific surface area and high conductivity, of the PS biochar. The stability of the PS@GCE sensor was also investigated in the presence of TC (10-4 M) and interfering species (10-2 M) and recovery rates in the range of 86.4%-116.0% were achieved, thus indicating the absence of an interference range of range of 84.3%-98.2% with relative standard deviation lower than 6% were achieved upon the detection of TC in natural water samples using the designed sensor, thus confirming the superior repeatability of the PS@GCE sensor. Consequently, the designed electrode has a high potential for application in the detection of TC in natural aqueous systems.

Analysis of electric field efficacy and remediation performance of triclosan contaminated soil by Co-Fe/al oxidation electrodes coupled with peroxymonosulfate (PMS) in an ECGO system with diversified electrode configurations.

Triclosan (TCS) is commonly used as a biocide against bacterial and fungal infections. The overuse of TCS has resulted in its abundance in the natural environment. Sulfate radicals have been used for in-situ groundwater remediation because of their superior performance. In this study, Co-Fe/Al oxidation electrodes were prepared to investigate the effect of electrode configurations on TCS remediation using electrokinetic geooxidation (ECGO) technology coupled with peroxymonosulfate (PMS) in a soil system. The Co-Fe/Al electrodes catalyzed the activity of PMS by solid-phase Co2+ to produce sulfate radicals. Four electrode configurations, named G1-G4, applying a potential gradient of 2 V/cm, were conducted for ten days in all experiments. Results showed that 14.2-66.2% of TCS remediation efficiency was observed. TCS was mainly degraded by the Co-Fe/Al electrode and sulfate radicals rather than being removed by the electroosmotic flow. The degradation efficiencies of the G4 system (66.0%) and the G2 or G3 system (36.6% or 64.4%, respectively) were much higher than that of the G1 system. (13.5%). Three regions (effective, ineffective, and enhanced) were classified to explore the effect of the electric field on TCS remediation. The arrangement of the honeycomb cells was related to the area of enhanced region in the system, in which the superior remediation performance of the TCS was found. Therefore, TCS remediation performance is highly related to the electrode configuration and honeycomb arrangement in the system. The seven-unit honeycomb system (G4) demonstrated a linear and centralized arrangement, resulting in fast migration and excellent degradation of the TCS.

Adsorption of Selected Pharmaceutical Compounds onto Activated Carbon in Dilute Aqueous Solutions Exemplified by Acetaminophen, Diclofenac, and Sulfamethoxazole.

The adsorption of three pharmaceuticals, namely, acetaminophen, diclofenac, and sulfamethoxazole onto granular activated carbon (GAC), was investigated. To study competitive adsorption, both dynamic and steady-state adsorption experiments were conducted by careful selection of pharmaceuticals with various affinities and molecular size. The effective diffusion coefficient of the adsorbate was increased with decease in particle size of GAC. The adsorption affinity represented as Langmuir was consistent with the ranking of the octanol-water partition coefficient, K(ow). The adsorption behavior in binary or tertiary systems could be described by competition adsorption. In the binary system adsorption replacement occurred, under which the adsorbate with the smaller K(ow) was replaced by the one with larger K(ow). Results also indicated that portion of the micropores could be occupied only by the small target compound, but not the larger adsorbates. In multiple-component systems the competition adsorption might significantly be affected by the macropores and less by the meso- or micropores.