Amending polycyclic aromatic hydrocarbon (PAH)-contaminated soils with biochar may be cheaper and environmentally friendly than other forms of organic materials. This has led to numerous studies on the use of biochar to either bind or stimulate the microbial degradation of organic compounds in soils. However, very little or no attention have been paid to the fact that biochars can give simultaneous impact on PAH fate processes, such as volatilization, sorption and biodegradation. In this review, we raised and considered the following questions: How does biochar affect microbes and microbial activities in the soil? What are the effects of adding biochar on sorption of PAHs? What are the effects of adding biochar on degradation of PAHs? What are the factors that we can manipulate in the laboratory to enhance the capability of biochars to degrade PAHs? A triphasic concept of how biochar can give simultaneous impact on PAH fate processes in soils was proposed, which involves rapid PAH sorption into biochar, subsequent desorption and modification of soil physicochemical properties by biochar, which in turn stimulates microbial degradation of the desorbed PAHs. It is anticipated that biochar can give simultaneous impact on PAH fate processes in soils.
Magnetic activated carbon (MG-AC), a solid product made by dispersing magnetic substrates on AC, is gaining attention for the removal of heavy metals from wastewater due to its favorable physico-chemical properties such as enhanced surface area and magnetic properties, respectively. However, the effects of two contrasting substrates, i.e., metal solution and metal particles, for the synthesis of MG-AC to obtain enhanced magnetic property have not been considered. The MG-AC was prepared by incorporating Fe 3 O 4 into the AC from two different sources of iron: Fe 3 O 4 extracted from electric arc furnace slag and from a ferric chloride/ferrous sulfate solution, to produce magnetic palm kernel shell from slag (MG-PKSS) and magnetic palm kernel shell from iron suspension (MG-PKSF), respectively. The adsorbent samples were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, X-ray diffraction, electron microscopy, i.e., SEM and FESEM, energy-dispersive X-ray, nitrogen adsorption, vibrating sample magnetometer. The results showed that the MG-PKSF had a greater BET surface area of 257 m 2 g -1 , a pore volume of 0.1124 cc g -1 and higher magnetic properties with a magnetic saturation of 49.55 emu g -1 relative to the MG-PKSS. The FTIR spectrum of the MG-PKSF illustrated the intense OH bending at 1629 cm -1 which can be attributed to the presence of oxygen in the samples. The absorption bands at 1093 and 579 cm -1 indicated the presence of C-O stretching and metal-oxygen (M-O) bands due to the interaction of iron and oxygen. Therefore, the MG-PKSF presented better characteristics for heavy metal removal from wastewater relative to the MG-PKSS, thereby suggesting that the raw material (metal solution) for impregnation played a crucial role in enhancing the quality of the MG-AC.
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