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Biochar modification by metals and metal oxides is considered a practical approach for enhancing the adsorption capacity of anionic compounds such as phosphate (P). This study obtained paper mill sludge (PMS) biochar (PMSB) via a one-step process by pyrolyzing PMS waste containing ferric salt to remove anionic P from water. The ferric salt in the sludge was transformed into ferric oxide and zero-valent-iron (Fe0) in N2 atmosphere at pyrolysis temperatures ranging from 300 to 800 °C. The maximum adsorption (Qm) of the PMSBs for P ranged from 11.44 to 25.19 mg P/g. Adsorption is a spontaneous and endothermic process, which implies chemisorption. PMSB obtained at 800 °C (PMSB800) exhibited the best performance for P removal. Fe0 in PMSB800 plays a vital role in P removal via adsorption and coprecipitation, such as forming the ≡Fe–O–P ternary complex. Furthermore, the possible chemical precipitation of P by CaO decomposed from calcite (CaCO3; an additive of paper production that remains in PMS) may also contribute to the removal of P by PMSB800. Moreover, PMSBs can be easily separated magnetically from water after application and adsorption. This study achieved a waste-to-wealth strategy by turning waste PMS into a metal/metal oxide-embedded biochar with excellent P removal capability and simple magnetic separation properties via a one-step pyrolysis process.

Phosphate adsorption using metal-based biochar has awakened much attention and triggered extensive research. In this study, novel Ca/Fe-rich biochars were prepared via a one-step process of pyrolyzing paper mill sludge (PMS) at various temperatures (300, 500, 700, and 800 °C) under a CO

Biochar is an effective amendment for trace metal/metalloid (TMs) immobilization in soils. The capacity of biochar to immobilize TMs in soil can be positively or negatively altered due to the changes in the surface and structural chemistry of biochar after soil application. Biochar surfaces are oxidized in soils and induce structural changes through physical and biochemical weathering processes. These changes in the biochar surface and structural chemistry generally increase its ability to immobilize TMs, although the generation of dissolved black carbon during weathering may increase TM mobility. Moreover, biochar modification can improve its capacity to immobilize TMs in soils. Over the short-term, engineered/modified biochar exhibited increased TM immobilization capacity compared with unmodified biochar. In the long-term, no large distinctions in such capacities were seen between modified and unmodified biochars due to weathering. In addition, artificial weathering at laboratories also revealed increased TM immobilization in soils. Continued collection of mechanistic evidence will help evaluate the effect of natural and artificial weathering, and biochar modification on the long-term TM immobilization capacity of biochar with respect to feedstock and synthesis conditions in contaminated soils.

The decomposition component analysis method can be used to monitor and diagnose the insulation state of SF6 electrical equipment in power industry. Here, the authors firstly compared the advantages and disadvantages of various SF6 decomposition products detection methods and analysed their feasibility of online monitoring. Then the requirements of SF6 decomposition products online detecting technology according to the actual engineering needs were discussed. The SF6 decomposition products online detection system has been mainly introduced from the aspects of principle, structure, detection effect, and practicability. The research points and development tendency of SF6 decomposition products online detection system is forecasted.

In recent years, C 4 F 7 N has been highly concerned due to its excellent dielectric performance and arcquenching ability. As a potential alternative to SF 6 , the decomposition characteristics of C 4 F 7 N will directly affect its application prospects. However, there are few studies on the decomposition characteristics of C 4 F 7 N mixed gas. Therefore, we conducted AC discharge breakdown experiment and partial discharge experiment on C 4 F 7 N-CO 2 mixed gas, and analyzed the gas decomposition by-products of C 4 F 7 N-CO 2 mixed gas qualitatively and quantitatively by using gas chromatography-mass spectrometry (GC/MS). The results show that the major decomposition by-products under AC discharge breakdown are CO, CF 4 , C 2 F 4 , C 2 F 6 , C 3 F 8 , CF 3 -CN, C 3 F 6 , C 4 F 6 , C 4 F 10 , C 2 F 5 -CN, C 2 N 2 , HCN, C 2 F 3 CN. Under partial discharge, the major decomposition byproducts are CO, CF 4 , C 3 F 8 , CF 3 -CN, C 3 F 6 , C 4 F 10 , C 2 F 5 -CN, C 2 N 2 , HCN, C 2 F 3 -CN. Compared with the partial discharge process, AC discharge breakdown produces more types of decomposition by-products. Besides, AC breakdown tends to produce smaller molecular by-products, while partial discharge tends to produce larger molecular by-products.

Anionic contaminants in water, groundwater, or wastewater are from both anthropogenic activities and geological release. Anionic contaminants in water can cause harm to organisms and the environment, even under low concentration conditions. Biochar, as a promising sorbent for environmental remediation, has been widely studied and evaluated. In this chapter, the adsorption capabilities of anionic contaminants by biochar and engineered/modified biochar are summarized. Pore filling, hydrogen bonding, surface complexation/precipitation, electrostatic attraction, and π–π interaction are the main mechanisms for biochar’s adsorption of anionic contaminants. The adsorption behavior of anionic contaminants is significantly affected by pH values, competition of coexisting ions, and environmental temperature. Although biochar has proven to be effective for anionic contaminants removal in water, evaluations, especially for the release of chemicals from biochar, are still needed before possible application in water/wastewater management.

In order to study the relationship between SF 6 gas decomposition components and the strength of PD caused by the metal protrusions defect inside the DC gas insulated electrical equipment, the DC SF 6 PD decomposition experiment was carried out for 96h under different discharge quantity in this paper, using the needle plate electrode to simulate the metal protrusion defect. The DC PD quantity was detected by the pulse current method. The paper obtained the growth regularity of SF 6 decomposition components under different DC PD quantity. The results show that the stable decomposition components of SF 6 under the negative DC PD include CF 4 , CO 2 , SO 2 F 2 , SOF 2 , SO 2 and so on. The generation amount relationship between the five gas compositions is CF 4 2 2 2 F 2 2 . SO 2 F 2 and SOF 2 are the main decomposition products of SF 6 under DC PD, the content of which is much higher than the other three. The DC PD quantity affects the concentration of these products significantly. The concentration of CO 2 , SO 2 F 2 , SOF 2 correlates well with Q sec . The concentration of these components increases continuously with the discharge time under the different Q sec . The generation speed γ m of SO 2 F 2 , SOF 2 and (SO 2 F 2 +SOF 2 +SO 2 ) linearly increases with Q sec roughly, which can be the characteristics of DC PD quantity.