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This work aimed to develop a feasible technology to reuse dead pig biowaste for heavy metals removal, which was first carbonized into pig bone char (PBC) after pyrolysis and further functionalized with amino (NH 2) to improve its affinity with heavy metals. The application of PBC after NH 2 -functionalization for aqueous heavy metals removal was explored, including Pb2+, Cu2+, and different complex Cu(II) species. PBC@SiO 2 -NH 2 showed comparable performance with AC@SiO 2 -NH 2. The adsorption capacity of Pb2+ and Cu2+ by PBC@SiO 2 -NH 2 was 120 and 30 mg g−1, respectively. The NH 2 functionalization enhanced the adsorption of complex Cu(II) species, and PBC@SiO 2 -NH 2 exhibited good performance under a wide pH range and coexisting ions. The adsorption of Cu(II) EDTA species with an EDTA/Cu(II) molar ratio of 1.0 by PBC would be enhanced ~3 times and ~6 times after NH 2 functionalization and further addition of Fe3+, respectively. The results of EDX, elemental mapping, and XPS confirmed the adsorption of Cu(II) species. The adsorption kinetics, isotherm, and thermodynamics of different Cu(II) species by PBC@SiO 2 -NH 2 were investigated. The regeneration of PBC@SiO 2 -NH 2 was easily performed via acidic wash. These results suggested the application potential of the reuse of biowaste, which could be a promising adsorbent for aqueous heavy metals after specific functionalization. [ABSTRACT FROM AUTHOR]

Magnetic biochar is increasingly known as a multi-functional material and the appropriate synthesis method further increase its efficient applications. In this study, the effects of synthesis methods on the fabrication of Kans grass straw/biochar (KGS/KGB) with Fe 3+ /Fe 2+ by chemical co-precipitation and subsequently pyrolyzing at 500 °C for 2 and 4 h were studied in details, and compared their As(III, V) adsorption potentials under different operating conditions. Magnetic biochars (MKGB3 and MKGB4) prepared from KGS revealed of superior Fe 3 O 4 loading, higher As(III, V) adsorption efficiency and saturation magnetization (45.7 Am 2 kg −1 ) than that of KGB (MKGB1 and MKGB2). Moreover, Thermogravimetric analysis (TGA) demonstrated three stages of decomposition and the MKGB3 and MKGB4 generated higher residual mass (>60%) at stage 3 (1000 °C) due to greater Fe 3 O 4 composite in biochar matrix and turned to be thermally more stable. As(III) and As(V) adsorption equilibrium data well fitted in Langmuir model and followed the order: MKGB4 > MKGB3 > MKGB2 > MKGB1. The maximum As(III) and As(V) adsorption capacities were about 2.0 mg g −1 and 3.1 mg g −1 , respectively. The data best fitted in pseudo-second-order ( R 2 > 0.99) rather than pseudo-first-order kinetics model indicating of more complex mechanism. The adsorption of As(III) and As(V) was found to decrease with increasing in ionic strength of competing ions and PO 4 3− was found to strongly inhibit arsenic adsorption. Highest desorption was achieved at pH 13.5 using NaOH. This study suggests that selective adsorbent synthesis method could be useful to prepare effective adsorbent for toxic metals immobilization. [ABSTRACT FROM AUTHOR]

Highlights: [•] Arsenic removal performance of SSFs containing HBC and Fe-HBC (50% w/w) is studied. [•] Over 99% and 98% arsenic removals were achieved in SSF(a) and SSF(b) under oxic-environment. [•] Two steps in situ mechanism is proposed to convert As(III) into As(V) and subsequent adsorption. [•] Low levels of influent co-occurring ions did not significantly interfered arsenic removal. [•] Filter with low-cost adsorbents could be proposed as feasible and efficient method for arsenic removal. [ABSTRACT FROM AUTHOR]

Abstract: Water pollution caused by ammonia nitrogen has attracted a great attention as its toxicity affects both the environment and human health. The objective of this paper was to investigate the adsorption behavior of NH4 +-N from aqueous solution by activated carbons prepared from rice husk. The physico-chemical properties of the activated carbon were characterized by Brunauer-Emmett-Teller (BET) test, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). It was found that the NH4 +-N adsorption on the rice husk derived carbons was dependent on adsorbent dosage and solution pH. The adsorption kinetics and isotherms of NH4 +-N by rice husk carbon were also investigated, and good correlation coefficients were obtained for the pseudo-second order kinetic equation. Dubinin-Radushkevitch (D-R) adsorption isotherm model could better describe the adsorption behavior of NH4 +-N on the rice husk carbon. Calculated by D-R model, the adsorption course of NH4 +-N on the rice husk carbon was favored chemical ion-exchange mechanism. Moreover, the activated carbon adsorbed NH4 +-N was highly fertilizer conservation especially for the nitrogen element. It was proposed that the amount of removed NH4 +-N from aqueous solutions would increase evidently treated by rice husk carbon if combined with biological method. [Copyright &y& Elsevier]

Abstract: Nanoscale Pd/Fe particles were combined with multi-walled carbon nanotubes (MWNTs) to prepare supported particles (MWNT-stabilized Pd/Fe), which were used to remove 2,4-dichlorophenol (2,4-DCP). The adsorption capacity of MWNTs was found to be increased with the increasing amount of chlorine atoms, and the removal rates of phenol (P), 2-chlorophenol (2-CP), 4-chlorophenol (4-CP) and 2,4-DCP reached 19.7%, 60.5%, 72.0% and 95.1% respectively, in 1min by MWNTs due to π–π interaction. The adsorption kinetics and adsorption isotherm were also discussed. MWNTs as a supporter, was effective for avoiding the agglomeration of nZVI. Furthermore, the speedy removal efficiency of the initial substances (2,4-DCP) reached about 50% in 1min, and over the time continued to rise to 100%, remaining low concentrations (<1mgL−1) of the intermediate substances (o-CP, p-CP), and gradual release of the final substance (P) from MWNT-stabilized Pd/Fe composites during the whole process, proposed a novel method for in situ remediation technology. [Copyright &y& Elsevier]

Abstract: Acid treatment is a routine demineralization process to obtain black carbon (BC), but there has been little systematic research about its influence on BC’s characteristics. In this study, elemental analysis, SEM, FTIR, and Boehm titration were used to investigate that effect. Our results showed that the acid treatment had little influence on the sorption of fly ash and soot to pentachlorophenol (PCP), but it greatly increased the sorption of rice chars to PCP. There were two competing effects of acid demineralization on the adsorption capacity of BC. On one hand, it increased the amount of the acidic functional groups, which decreased the adsorption capacity. On the other hand, it increased the surface and pore volume of BC and caused the emergence of hidden carbon enclosed by minerals, which in turn increased the sorptivity significantly. Especially for rice chars (600°C), after acid treatment, their surface area increased from 3.52 to 235m2 g−1 and the sorption capacity coefficient increased from 2.12 to 4.10. [Copyright &y& Elsevier]

Abstract: The adsorption of Cu(II) from aqueous solution by carbons prepared from rice husk through pyrolysis and steam activation was studied. The rice husk carbon was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and its pore structure was also examined. After comparing different characteristics of the carbons prepared under different conditions and their adsorption abilities of Cu(II), the optimum temperature for pyrolysis and steam activation was chosen as 700 and 750°C, respectively, using 3% (V/V) steam as the best activation gas. It was found that the Cu(II) adsorption on the rice husk derived carbons was pH and temperature dependent with an optimum pH value of 5.0, and an equilibrium time of 24h. The adsorption kinetics and isotherms of Cu(II) by the rice husk derived carbons were also investigated under four different temperatures, and good correlation coefficients were obtained for the pseudo-second-order kinetic models, and the Langmuir isotherm model fitted very well with the experimental data. The mean free energy E (kJmol−1) obtained in the Dubinin-Radushkevitch (D-R) adsorption isortherm equation indicated a chemical ion-exchange mechanism. Several thermodynamic parameters were also caculated to predict the nature of adsorption process. [ABSTRACT FROM AUTHOR]