Green Analytical Chemistry (Sep 2023)
Peanut shell-derived activated biochar as a convenient, low-cost, ecofriendly and efficient sorbent in rotating disk sorptive extraction of emerging contaminants from environmental water samples
Abstract
The use of agricultural byproducts for the development of new sorbent phases has become increasingly popular among the scientific community of analytical chemists due to the intrinsic properties of these materials, including biodegradability, nontoxicity and biocompatibility. In the current research, peanut shells, peanut shell biochar and activated carbon were assessed as microextraction sorptive phases by using rotating disk sorptive extraction of emerging contaminants covering a range of polarities (ethyl paraben, diclofenac, triclosan, bisphenol A, and 17-α-ethinylestradiol) and subsequent detection by gas chromatography coupled to mass spectrometry (GC–MS). It was demonstrated that, independent of the polarity of the analyte, the extracting capacities of the activated carbon were superior to those of biochar and the untreated phase.The three sorptive phases were characterized by different techniques. SEM micrographs show the absence of pores in the untreated phase, which changes substantially after pyrolysis. The activated carbon exhibited a BET area of 516 m2 g−1 and a pore size and total pore volume of 2.12 nm and 0.27 cm3 g−1, respectively. The high porosity and some characteristic signals in the FTIR spectra suggest that the main interactions of activated carbons with analytes are pore filling and π-π stacking.Optimization studies showed that the optimal conditions for extraction were 10 mg of sorptive phase, pH 2, 70 min of extraction time, 15 mL of sample volume, 2000 rpm rotating velocity, and ethyl acetate as the elution solvent. The validation showed limits of detection between 0.003 and 0.729 µg L−1, absolute recoveries ranging between 16 and 87% and relative standard deviations below 10%. A comparative study using the same extraction technology but with commercial phases demonstrated that activated carbon achieves comparable or higher extraction efficiencies for this set of analytes.
