Oxidative degradation of dinitrotoluenes (DNTs) in wastewater was performed using persulfate anions combined with ultrasonic irradiation, wherein a synergistic effect is observed. The batch-wise experiments were carried out to elucidate the influence of various operating parameters on sono-activated persulfate oxidation, including ultrasonic power intensity, persulfate anion concentration, reaction temperature and acidity of wastewater. It is noteworthy that the nitrotoluene contaminants could be almost completely eliminated by virtue of sono-activated persulfate oxidation, wherein sulfate radicals serve as principal oxidants, of which amounts are significantly enhanced via addition of sodium sulfate. Based on the results given by gas chromatograph-mass spectrometer (GC-MS), it is postulated that the methyl group of DNTs preliminarily underwent oxidation pathway into dinitrobenzoic acid, followed by decarboxylation to form 1,3-dinitrobenzene (DNB). In sum, the sono-activated persulfate oxidation is a promising method for treatment of nitrotoluenes in wastewater.

In this work, the cocoa pod husk (CPH) was converted into biochar products at higher carbonization temperatures (i.e., 400–800 °C). The pore and chemical properties of the resulting biochars and its post-leaching biochars by acid washing, including specific surface area, total pore volume, pore size distribution, true density, and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and Fourier Transform infrared spectroscopy (FTIR) were studied. Based on the pore properties, pyrolysis temperature at around 800 °C seemed to have the most profound impact on the pore development for producing biochar, where its Brunauer–Emmet–Teller (BET) surface area is 101 m²/g. More noticeably, more pores in the CPH-based biochar could be significantly created during the acid-washing, resulting in an increase of BET surface area from 101 to 342 m²/g. According to the data on the EDS and FTIR, the resulting biochars seemed to have oxygen-containing functional groups on the surface. Furthermore, the methylene blue (MB) adsorption performance of the optimal biochar product with maximal BET surface area was tested to fit its kinetics by the pseudo-second order model, showing a strong interaction between the biochar adsorbent and the cationic adsorbate.