The significant role of electron donating capacity and carbon structure of biochar to electron transfer of zerovalent iron.

Herein, the major biochar properties were correlated with electron transfer of zerovalent iron (ZVI) and contribution of biomass constituents to biochar property was ascertained to optimize electron transfer of ZVI. To this end, five respective stalk-type and wood-type lignocellulosic biomasses were pyrolzed at 600 °C to prepare biochars to harbor ZVI (ZVI/BC). Thermogravimetric analysis demonstrated woody biomasses decomposed more intensively at higher temperature relative to stalky biomass. ZVI/BC were characterized with Raman, X-ray diffraction, and electrochemical analyses including electron donating capacity (EDC) and electron accepting capacity (EAC). Pearson correlation and partial least-squares (PLS) analyses confirmed that Cr(VI) reduction capacity was negatively related to Tafel corrosion potential and intensity ratio of ID/IG, but significantly positively-related to EDC of BC, in which EDC was a predominant attribute to contribute to reductive capacity toward Cr(VI) reduction. That is, greater EDC and higher graphitic carbon structure of biochar due to cellulose and hemicellulose components favor electron transfer of ZVI toward Cr(VI) reduction.

A fast analytical protocol for simultaneous speciation of arsenic by Ultra-High Performance Liquid Chromatography (UHPLC) hyphenated to Inductively Coupled Plasma Mass Spectrometry (ICP-MS) as a modern advancement in liquid chromatography approaches.

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) hyphenated to High Performance Liquid Chromatography (HPLC) and Ion Chromatography (IC) are widely used for simultaneous speciation of arsenic (As). Longer retention time resulting in a slow separation is the major drawback of these existing approaches. Besides, fast separations achieved from HPLC based methods have always resulted in poor resolution and baseline separation between peaks. For the first time, the present study aimed to improve the existing HPLC related methods in order to develop a fast analytical protocol based on Ultra-High Performance Liquid Chromatography (UHPLC) hyphenated to ICP-MS detection for simultaneous separation and quantification of arsenite (As(III)), arsenate (As(V)), dimethylarsonate (DMA(V)) and monomethylarsenate (MMA(V)). Two types of ammonium-based mobile phases (i.e. NH4H2PO4 and NH4NO3) were examined at different eluent concentrations and pH to choose the most effective eluent system. Results demonstrated that the mixed mobile phase containing 8.5 mM of NH4H2PO4 and NH4NO3 (1:1) at pH 6.0 is the most effective eluent achieving the separation of As species with improved resolutions within 5 min which is almost a double saving in analysis time per sample compared to the existing methods (9-15 min). Faster separation is analytically cost effective in terms of ICP-MS running cost and energy consumption. Unlike HPLC, UHPLC did not generate a higher column back pressure with increasing flow rate up to 2.5 mL/min resulting in a faster separation with excellent resolution of peaks. Limits of detection for As species were in the range of 0.3-0.5 µg/L. The proposed method was applied to quantify As species present in commercially available rice varieties in Australia and Sri Lanka. Results of speciation analysis indicated that As(III) is the dominant species, ranging from 53 to 100% in the rice grains. The proposed analytical protocol based on UHPLC-ICP-MS provided an accurate and reliable identification and quantification of As species with the advantages of rapid separation, excellent resolution, and low detection limits. Such a recent trend in fundamental research could be a turning point for future environmental and biological research to further improve this strategy for the speciation of other toxic metal(loid)s in food, water and biological samples.