Rice Husk Biochars Modified with Magnetized Iron Oxides and Nano Zero Valent Iron for Decolorization of Dyeing Wastewater

This study investigated if biochar, a low-cost carbon-rich material, can be modified with reactive materials for decolorization of dyeing wastewater. Two types of rice husk biochars were produced by using different processes of gasification and pyrolysis in limited air condition. The biochars were first magnetized and then modified with nano-scale zero-valent iron (nZVI) to achieve the final products of magnetic-nZVI biochars. Batch experiments were conducted to investigate the efficiency of the modified biochars for reducing color of the reactive dyes yellow (RY145), red (RR195), and blue (RB19) from dyeing solutions. Results showed that color removal efficiency of the modified biochars was significantly enhanced, achieving the values of 100% for RY145 and RR195 and ≥65% for RB19, while the effectiveness of the original biochar was significantly lower. In addition, with increasing dose of the modified biochars, the color removal efficiency increased accordingly. In contrast, when the dose of nZVI was increased beyond a certain value then its color removal efficiency decreased accordingly. It is reported that the magnetic-nZVI rice husk biochars effectively removed the reactive dyes. The impregnation of nZVI particles on the biochar surface spatially separates the nZVI particles, prevents its aggregation and therefore enhances the decolorization efficiency.

本研究探讨了生物炭（一种低成本的富碳材料）是否可通过活性材料改性用于印染废水脱色。在有限空气条件下，采用气化和热解两种不同工艺制备了两种稻壳生物炭。首先将生物炭磁化，然后用纳米零价铁（nZVI）进行改性，得到磁性 - nZVI生物炭最终产物。通过批量实验研究了改性生物炭对印染溶液中活性染料黄（RY145）、红（RR195）和蓝（RB19）的脱色效率。结果表明，改性生物炭的脱色效率显著提高，RY145和RR195的脱色率达到100%，RB19的脱色率≥65%，而原始生物炭的效果则明显较低。此外，随着改性生物炭投加量的增加，脱色效率相应提高。相反，当nZVI的投加量超过一定值时，其脱色效率相应降低。据报道，磁性 - nZVI稻壳生物炭可有效去除活性染料。nZVI颗粒在生物炭表面的负载使其在空间上分离，防止了其团聚，从而提高了脱色效率。