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Magnetic modified-corncob biochar with an impregnation ratio of iron at 20% (w/w) was used for removal of Cr(VI) from aqueous solution. Batch adsorption experiments were conducted to investigate the adsorption isotherm, kinetics and mechanism of Cr(VI) onto MCB20. The results indicated that the maximum adsorption capacity achieved was 25.94 mg g−1. The adsorption kinetic data were found to fit best to the pseudo-second order model with a high correlation coefficient (R2 = 0.992). The adsorption mechanisms of Cr(VI) onto MCB20 were electrostatic attraction, anion exchange and adsorption coupled-reduction. The adsorption mechanisms occurring between Cr(VI) anions and MCB20 were due to mainly the contribution of Fe3O4 present in the corncob biochar structure after magnetization by FeCl3. Among the aforementioned mechanisms, adsorption coupled-reduction plays a vital role in removal of Cr(VI) by enhancement of the reduction of Cr(VI) to Cr(III) through generation of electron-donor groups (hydroxyl groups) on the MCB20 surface. Then, Cr(VI) interacted with the electron-donor groups and Cr(VI) is reduced to Cr(III). Besides, Fe2+ ions in the MCB20 structure were simultaneously oxidized to Fe3+ ions and enhanced the transformation of Cr(VI) into Cr(III). The reduced Cr(III) cations, finally, were adsorbed by MCB20 through substitution of Fe3+ with Cr3+ under acidic conditions, complexation with surface functional groups of MCB20 and formation of Cr(OH)3. This study both developed a new way to produce a low cost adsorbent for removal of Cr(VI) from aqueous solution and solved waste by waste. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is one of the most toxic heavy metals and a non‐essential element to all organisms, including plants; however, the genes involved in Cd resistance in plants remain poorly characterised.To identify Cd resistance genes in rice, we screened a rice cDNA expression library treated with CdCl2 using a yeast (Saccharomyces cerevisiae) mutant ycf1 strain (DTY167) and isolated two rice phytochelatin synthases (OsPCS5 and OsPCS15).The genes were strongly induced by Cd treatment and conferred increased resistance to Cd when expressed in the ycf1 mutant strain. In addition, the Cd concentration was twofold higher in yeast expressing OsPCS5 and OsPCS15 than in vector‐transformed yeast, and OsPCS5 and OsPCS15 localised in the cytoplasm. Arabidopsis thaliana plants overexpressing OsPCS5/‐15 paradoxically exhibited increased sensitivity to Cd, suggesting that overexpression of OsPCS5/‐15 resulted in toxicity due to excess phytochelatin production in A. thaliana.These data indicate that OsPCS5 and OsPCS15 are involved in Cd tolerance, which may be related to the relative abundances of phytochelatins synthesised by these phytochelatin synthases. [ABSTRACT FROM AUTHOR]