Global wastewater pollution issues demands developing innovative and cost-efficient techniques for wastewater treatment. The current study reports application of different metal oxide (iron, copper, zinc) doped carbon-based materials such as activated carbon (AC), groundnut shell (GS), cotton stalk (CS) and biochar (BC) for the removal of methylene blue (MB). Iron oxide-doped AC exhibited significantly higher adsorption capacity (∼32 mg/g) with all the other metal oxide-doped AC having the adsorption capacity below ∼10 mg/g. Adsorption of MB on FeCS followed the Freundlich isotherm, suggesting multilayer adsorption on the heterogeneous active sites. Kinetic models indicated dominant chemisorption mechanisms, aligning well with the pseudo-second-order model. Higher adsorption capacity under alkaline pH conditions is attributed to the prevalence of negative charges on the surface. The presence of ultrasound further intensified the adsorption behavior resulting in a maximum removal efficiency of ∼90 % within 10 min. An optimum adsorbent loading of 0.5 g/L was determined for effective removal of MB. FeCS adsorbent displayed stable performance over multiple cycles, affirming its reliability for reuse. These results shed light on the practical application of biochars derived from large scale pyrolysis process for the wastewater remediation.

全球废水污染问题需要开发创新且经济高效的废水处理技术。目前的研究报道了不同金属氧化物（铁、铜、锌）掺杂的碳基材料如活性炭（AC）、花生壳（GS）、棉秆（CS）和生物炭（BC）用于去除亚甲基的应用蓝色（MB）。氧化铁掺杂的活性炭表现出明显更高的吸附容量（~32 mg/g），而所有其他金属氧化物掺杂的活性炭的吸附容量低于~10 mg/g。MB 在 FeCS 上的吸附遵循 Freundlich 等温线，表明异质活性位点上有多层吸附。动力学模型表明了主要的化学吸附机制，与伪二阶模型非常吻合。碱性 pH 条件下较高的吸附能力归因于表面负电荷的普遍存在。超声波的存在进一步强化了吸附行为，导致 10 分钟内最大去除效率达到 90%。确定有效去除 MB 的最佳吸附剂负载量为 0.5 g/L。FeCS 吸附剂在多个循环中表现出稳定的性能，证实了其重复使用的可靠性。这些结果揭示了大规模热解过程中产生的生物炭在废水修复中的实际应用。