FeS and Fe3O4 Co-modified biochar to build a highly resistant advanced oxidation process system for quinclorac degradation in irrigation water.

Advanced oxidation processes (AOPs), based on sulfate radical (SO4·-) produced by peroxymonosulfate (PMS), can effectively mineralize refractory organic pollutants. However, the coexistence of anions and natural organic matters in actual wastewater prevents the application of AOPs. A simple one-step method was used to prepare FeS/Fe3O4 co-modified biochar materials (FFB) that could activate PMS to degrade quinclorac (QNC) with a removal rate of 100%, even exhibiting optimum degradation of QNC reached 99.31% in irrigation water, demonstrating excellent anti-interference performance for co-existing anions and natural organic matter. Meanwhile, ecotoxicity analysis showed that the toxicity of degradation intermediates was lower than that of QNC. Characterization results demonstrated the even distribution of FeS and Fe3O4 onto biochar, supplying abundant Fe2+ to activate PMS producing reactive oxygen species (ROS), while the generated Fe3+ after reactive continue to be reduced with sulfur species to promote the cycle of Fe2+/Fe3+. The coexistence of ·OH, SO4·-, 1O2, and O2·- in the FFB/PMS-QNC system suggest the possession of two pathway with free radical and non-free radical pathways to degrade QNC. The density functional theory (DFT) was used to analyze the adsorption sites and adsorption energy of PMS, as well as the differential charge density, which further proved the generation of SO4·-, O2·- and 1O2. In addition, the electrochemical test results showed that electron transfer also played an important role in the degradation of QNC. This study provides a feasible approach for the removal of organic pollutants in actual water.

Oxygen-limited pyrolysis and incineration impact on biochar transport.

At present, studies on biochar transport have focused on biochar obtained by oxygen-limited pyrolysis, which may differ from conventional biochar produced by incineration in nature. This work investigated the transport and retention mechanisms of three types of oxygen-limited pyrolytic biochar and three types of traditional biochar in saturated porous media. The results showed that the specific surface area of the three oxygen-limited pyrolysis biochar (180-200 m2·g-1) was higher than that of the traditional biochar (50-60 m2·g-1). Therefore, the retention capacity of pyrolytic biochar is strong and the permeability is less than 0.1. The absolute value of the zeta potential of traditional biochar is greater than 30 mV, and the electrostatic repulsion generated is stronger, with a peak penetration rate of 0.16. Moreover, the zeta potential of biochar and traditional biochar is regulated by pH value and ionic strength. In acidic conditions or solutions with high ionic strength, the zeta potentials of the six types of biochar changed to about - 15 mV, and the second minimum value was less than 0, indicating that there was a tendency for sedimentation. This study provides a new perspective for assessing the transport and environmental risks of biochar in the environment.

Rice husk biochar mediated red phosphorus for photocatalysis and photothermal removal of E. coli.

The current photocatalytic bactericidal materials in the field of food pathogen control are usually consisted of metals that always suffering from poor stability and possible secondary pollution. Besides, the requirement for high energy excitation also inspires the enthusiasm on exploring non-metallic catalysts. Herein, the non-metallic composite of rice shell biochar loaded with red phosphorus (B@RP) was developed for photocatalysis and photothermal removal of bacteria. The B@RP showed effective photocatalysis performance to stimulate the generation of OH and O2- free radicals for the elimination of Escherichia coli (E. coli). At the same time, the photothermal effect of B@RP can also increase the permeability of cell membrane, which is conducive to free radicals entering the cell interior. Therefore, the non-metallic composite could achieve complete removal of E. coli within 2 h under illumination. Meanwhile, B@RP had excellent stability and the sterilization efficiency maintained 100% after 9 cycles. Hence, B@RP is expected to be a harmless and efficient bactericidal material for food industry.