Abstract It is of great significance to remove Cr(VI) from water as a result of its high toxicity. Biochar from corn straw was modified by different acids (HNO3, H2SO4 and H3PO4) to remove Cr(VI) from aqueous solution. To estimate the removal mechanisms of Cr(VI) by the acid-modified biochars, batch experiments were performed in the light of contact time, Cr(VI) concentration, and pH, and the characteristics of acid-modified biochars before and after Cr(VI) adsorption were investigated by Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS). The adsorption kinetics of Cr(VI) by acid-modified biochars were consistent with the pseudo-second-order model, and the adsorption isotherm obeyed the Freundlich model. Furthermore, the acid- modified biochars could supply more oxygen-containing functional groups (-COOH and -OH) as electron donor (e−) and hydrogen ion (H+) to enhance the reduction of Cr(VI) to Cr(III), resulting in enhanced removal of Cr(VI). HNO3-modified biochar exhibited the highest removal efficiency of Cr(VI). In general, the acid modifition of biochar was an effective method to increase the removal of Cr(VI).

中文翻译：

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玉米秸秆不同酸改性生物炭强化去除六价铬：行为与机制

摘要由于Cr(VI)具有高毒性，去除水中的Cr(VI)具有重要意义。采用不同的酸（HNO3、H2SO4 和 H3PO4）对玉米秸秆中的生物炭进行改性，以去除水溶液中的 Cr(VI)。为了评估酸改性生物炭对 Cr(VI) 的去除机制，根据接触时间、Cr(VI) 浓度和 pH 值以及酸改性生物炭在 Cr(VI) 处理前后的特性进行了批量实验。 VI)通过傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)研究吸附情况。酸改性生物炭对Cr(VI)的吸附动力学符合准二级模型，吸附等温线服从Freundlich模型。此外，酸改性生物炭可以提供更多的含氧官能团（-COOH和-OH）作为电子供体（e-）和氢离子（H+），以增强Cr（VI）还原为Cr（III），从而增强 Cr(VI) 的去除。HNO3 改性生物炭对 Cr(VI) 的去除效率最高。总的来说，生物炭的酸改性是提高Cr(VI)去除率的有效方法。