Soil washing is an efficient, economical, and green remediation technology for removing several heavy metal (loid)s from contaminated industrial sites. The extraction of green and efficient washing agents from low-cost feedback is crucially important. In this study, a soluble humic substance (HS) extracted from leonardite was first tested to wash soils (red soil, fluvo-aquic soil, and black soil) heavily contaminated with arsenic (As) and cadmium (Cd). A D-optimal mixture design was investigated to optimize the washing parameters. The optimum removal efficiencies of As and Cd by single HS washing were found to be 52.58%–60.20% and 58.52%–86.69%, respectively. Furthermore, a two-step sequential washing with chemical reductant NH₂OH•HCl coupled with HS (NH₂OH•HCl + HS) was performed to improve the removal efficiency of As and Cd. The two-step sequential washing significantly enhanced the removal of As and Cd to 75.25%–81.53% and 64.53%–97.64%, which makes the residual As and Cd in soil below the risk control standards for construction land. The two-step sequential washing also effectively controlled the mobility and bioavailability of residual As and Cd. However, the activities of soil catalase and urease significantly decreased after the NH₂OH•HCl + HS washing. Follow-up measures such as soil neutralization could be applied to relieve and restore the soil enzyme activity. In general, the two-step sequential soil washing with NH₂OH•HCl + HS is a fast and efficient method for simultaneously removing high content of As and Cd from contaminated soils.

土壤清洗是一种高效、经济、绿色的修复技术，用于去除受污染工业场地中的多种重金属（类固醇）。从低成本反馈中提取绿色高效的洗涤剂至关重要。在这项研究中，首先测试了从风化褐煤中提取的可溶性腐殖质 (HS) 以清洗被砷 (As) 和镉 (Cd) 严重污染的土壤（红土、潮土和黑土）。研究了 D 最优混合设计以优化洗涤参数。单次 HS 洗涤对 As 和 Cd 的最佳去除效率分别为 52.58%–60.20% 和 58.52%–86.69%。此外，采用化学还原剂 NH ₂ OH•HCl 与 HS (NH ₂OH•HCl + HS)提高了As和Cd的去除效率。两步顺序冲洗显着提高了As和Cd的去除率，达到75.25%~81.53%和64.53%~97.64%，使土壤中残留的As和Cd低于建设用地风险控制标准。两步顺序洗涤还有效地控制了残留 As 和 Cd 的流动性和生物利用度。然而，NH ₂ OH•HCl + HS洗涤后土​​壤过氧化氢酶和脲酶活性显着降低。可以采取土壤中和等后续措施来缓解和恢复土壤酶活性。_{一般来说，NH 2}两步顺序洗土OH•HCl + HS 是一种快速有效的方法，可同时去除污染土壤中高含量的 As 和 Cd。