This study investigated the removal of heavy metal ions from industrial wastewater by using rice and corn husk biochar. The choice of the materials was influenced by their large surface area, abundance of functional groups as well as their availability in the local environment. Rice and corn husks were pyrolyzed at 500, 600, and 700 °C to make biochars that were used to treat low-quality industrial wastewater. Initial metal ion levels in wastewater and residual levels after the application of biochars were measured using an atomic adsorption spectrophotometer. Carbonization of rice husks at 600 °C produced the best removal efficiencies for Cr (65%), Fe (90%), and Pb (> 90%). The carbonization of corn husks at 600 °C produced the worst removal efficiencies for Cr (only 20%) and Pb (slightly > 35%). Regardless of the carbonization temperature, rice husk biochars performed better than corn husk biochars. Experimental data fitted well the Langmuir and Freundlich isotherm models (R² values ranging between 0.82 and 0.99). The Langmuir separation factor, R_L, had negative values, probably due to the low initial concentration of the adsorbates in the raw wastewater. All the biochars showed a relatively short contact time (20 to 30 min) to attain maximum adsorption efficiencies and are a promising feature for future industrial applications. The studied biochar materials from rice and corn husk have the potential to remove heavy metal ions from industrial wastewater; rice husk biochar showed higher removal capacity than corn husk biochars.

中文翻译：

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利用稻米和玉米皮生物炭去除工业废水中的重金属离子

这项研究调查了使用大米和玉米壳生物炭去除工业废水中重金属离子的方法。材料的选择受其较大的表面积，丰富的官能团及其在当地环境中的可用性的影响。稻壳和玉米壳在500、600和700°C高温下进行热解，制得生物炭，用于处理劣质工业废水。使用原子吸收分光光度计测量废水中的初始金属离子水平和施加生物炭后的残留水平。在600°C时，稻壳的碳化对Cr（65％），Fe（90％）和Pb（> 90％）的去除效率最高。玉米壳在600°C时碳化会导致Cr（仅20％）和Pb（略大于35％）的去除效率最差。不论碳化温度如何 稻壳生物炭的性能优于玉米壳生物炭。实验数据非常适合Langmuir和Freundlich等温模型（R ²值介于0.82和0.99之间。Langmuir分离因子R _L具有负值，这可能是由于原废水中吸附物的初始浓度较低。所有生物炭均显示出相对较短的接触时间（20至30分钟）以达到最大吸附效率，并且对于未来的工业应用而言，这是一个很有前途的功能。研究的稻米和玉米壳生物炭材料具有去除工业废水中重金属离子的潜力。稻壳生物炭比玉米壳生物炭具有更高的去除能力。