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[Display omitted] • Carbonization and crystallization of feedstock can be achieved by one step in Sc-CO 2. • Iron salt enhanced depolymerization of plastics significantly via catalytic effect. • Sc-CO 2 favored formation of oxygen-rich functional groups on magnetic hybrid surface. • Magnetic Fe 3 O 4 was in-situ anchored in formed carbonaceous pore of bulk char. • Halogen-free magnetic hybrid exhibited excellent capacity for Cr(VI) immobilization. A huge amount of waste halogenated plastics is a considerable resource pool but how to transform these wastes into functional products is always a great technical challenge due to potential release of halogenated dioxin during process. In this study, one type of benign reaction medium-sub/supercritical carbon dioxide (Sc-CO 2) was used for converting halogenated plastics into magnetic carbon-based hybrid along with simultaneous dehalogenation. It was found that Sc-CO 2 treatment coupled with subsistent iron salt adjuvant advantageously inhibited the generation of benzene derivatives with high molecular weight and facilitated growth of pore structure of carbon skeleton with limited production of coke tars. Meanwhile, magnetic Fe 3 O 4 particles were gradually crystallized and eventually encapsulated in ordered mesoporous carbonaceous product to enhance the further carbonization of plastics without any halide residues. Cr(Ⅵ) immobilization tests indicated that as-obtained magnetic hybrid exhibited great adsorption capacity above 157 mg g−1 and the immobilization process was well fit for Langmuir model and pseudo-second-order kinetic model. This study provides a new insight into a cost-effective process for fabrication of magnetic functional hybrid using waste halogenated plastics without release of second pollutants and its versatile application as adsorbents or catalysts. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a novel two-stage process, i.e. first stage for hydrogen species generation at 150°C and second stage for PCB dechlorination at 330°C, was developed for efficient PCB degradation in subcritical water with nanoscale Ni/Fe particles. The obtained results showed that over 92% of PCBs was completely converted into 1-alkyl-benzenes during this process. The addition of hydrogen donors could greatly enhance PCB dechlorination in descending order: oxalic acid≈HAc>NaH2PO4 ≈KH2PO4. The anion introduced along with H+ played the crucial role in overall dechlorination process due to the undesired reaction between anion and reactive nanoscale Ni/Fe. Oxalic acid was quite effective for the generation of hydrogen species by supply more available H+ without undesired side reaction. In contrast, phosphate could react with Ni/Fe rapidly to form complex precipitates on particle surface and thereby block the reactive sites of particle following suspension of dechlorination. In addition, low 150°C at first stage as compared to 330°C at second stage favored the dissolution and adsorption of hydrogen on Ni surface for catalyzing to form more reactive hydrogen species used for rapid dechlorination. [Copyright &y& Elsevier]

Abstract: Polychlorinated biphenyls (PCBs) are environmentally persistent, toxic, bioaccumulative and recalcitrant. In this study, aged PCBs from e-waste contaminated site were respectively subjected to Soxhlet and solvothermal treatments. The results indicated that solvothermal method was much more predominant for PCBs removal than traditional Soxhlet method. Sequential Soxhlet–solvothermal experiment demonstrated that Soxhlet unextractable (bound) PCBs were efficiently removed by solvothermal procedure due to enhanced solvating effects of organic solvents. The key point was that bound PCBs in the aged soil were partitioned in different components of soil organic matter, e.g., the solvothermal removal amounts of ∑I-VPCBs (sum of PCB8, PCB18, PCB28, PCB44, PCB66) from fulvic acid (FA), humic acid (HA), bound humic acid (bound HA), bound lipids and mineral fraction were 0.4, 40.8, 28.4, 19.8, and 10.6%, respectively. It was found that isopropanol was the most effective solvent for PCBs removal. The optimum performing temperature, time and liquid to solid ratio for PCB8, PCB18, PCB28, PCB44, and PCB66 were 170°C, 8h and 10:1, respectively. As for higher molecular weight PCB congeners, these conditions were 150°C, 10h and 15:1. Soil organic matter content was unchanged after solvothermal treatment indicating that soil fertility remained after the removal process. This work provides a more clean process for effective treatment of soils contaminated by persistent organic pollutants (POPs) in comparison to traditional methods. [Copyright &y& Elsevier]

Abstract: The present study was carried out to better understand the reactivity of nanoscale Ni/Fe particles towards the dechlorination of polychlorinated biphenyls (PCBs) contained in waste capacitor oil and the corresponding dechlorination mechanism in subcritical water. Batch experiments showed that nanoscale Ni/Fe particles could more quickly and effectively dechlorinate PCBs stepwise as compared to nanoscale zerovalent iron (n-ZVI) and nano-Ni0. The dechlorination products were much more centralized in the presence of Ni/Fe than other particles, and biphenyl, cyclohexyl-benzene and 1-alkyl-benzenes were the main products which can be used as raw chemicals. Moreover, catalytic hydrogenation by virtue of introduction of Ni0 as catalyst can not only result in rapid dechlorination but also avoid formation of toxic chlorinated hydrocarbons. The reactivity of nanoscale Ni/Fe can retain in subcritical water for rapid catalytic hydrodechlorination. This process poses the prospect of recovery of valuable chemicals in the course of disposal of hazardous PCB-containing capacitor oil or transformer oil. [Copyright &y& Elsevier]

A functionalized carbonaceous material was prepared via hydrothermal carbonization (HTC) of biogas residues and denoted as hydrochar (HC). The obtained HC was used to synthesize a hybrid (Ni/Fe-HC) to conduct Pb(II) removal from aqueous solution. SEM images show that Ni 0 /Fe 0 was anchored tightly to HC particles due to a cellular structure of HC formed during HTC. Complete Pb(II) removal (>99.5%) was achieved within 1.5 h using Ni/Fe-HC whereas more than 85% of Pb(II) remained in bulk solution after 10 h with bare HC. SEP results indicate that Pb(II) was mainly associated with the fraction bound to carbonates and Fe–Mn oxides in the spent Ni/Fe-HC particles. Consequently, the adsorptive precipitation and specific adsorption dominated Pb(II) removal by Ni/Fe-HC despite minor reduction of Pb(II) to Pb 0 . However, the reduction of Pb(II) to Pb 0 was conducted by the catalytically generated atomic hydrogen rather than Ni/Fe nanoparticles as electron donor. Ni/Fe-HC not only acted as an effective adsorbent for Pb(II) but also played a role of catalyst to generate atomic hydrogen. HC prepared with biogas residues can be used as an excellent supporting material to prepare a hybrid of Ni/Fe-HC for Pb(II) removal. [ABSTRACT FROM AUTHOR]

In this study, CoMnAl mixed metal oxides (CoMnAl-MMO) were prepared and employed in heterogeneous activation of Oxone for bisphenol A (BPA) degradation. Typically, 10 mg L −1 of BPA could be completely degraded under the coexistence of 0.02 g L −1 of CoMnAl-MMO and 0.15 g L −1 of Oxone within 90 min at 25 °C. The degradation performance was evaluated in view of metal leaching and various effects, e.g., pH, Oxone dosage and temperature. The results indicated that the system of MMO/Oxone was suitable for the treatment of wastewater and presented favorable recycling and stability in both neutral and alkaline conditions. It was confirmed that BPA degradation catalyzed by CoMnAl-MMO followed well with the first order kinetics model and the an activation energy was calculated as 76.83 kJ mol −1 . The sulfate radicals were recognized as the main species to oxidize pollutants in the MMO/Oxone system. Particular attention was paid to the catalysis activation mechanism of peroxymonosulfate and the degradation pathway of BPA, which were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopic (XPS), LC–MS and GC–MS. [ABSTRACT FROM AUTHOR]