The Improving of Cd 2+ Adsorption Performance of Hydrochar Obtained from Corn Straw Waste with KOH Activation

The corn straw hydrochar was prepared by a two-step method of hydrothermal carbonization and chemical activation. Hydrochar (HC) is a promising adsorbent due to its porous and abundant carbon structure. Chemical activation can improve the HC surface structure and properties and enhance the HC adsorption capacity. In this study, different concentrations of KOH solution were used to activate the original HC, improve the adsorption performance of the original HC, and efficiently remove Cd 2+ from the solution. The surface properties of activated hydrochar were characterized using SEM, FTIR, XPS, elemental analysis, and other methods. The results showed that the activation of KOH enriched the active sites of HC. Among them, the HC activated by 1 mol/L KOH has the best adsorption (31.40 mg/g), which is 5.38 times the original HC adsorption. After KOH activation, surface complexation and ion exchange were enhanced, which facilitated the removal of Cd 2+ . Therefore, KOH activation of HC is an efficient and easy-to-operate method to convert straw hydrochar into an adsorbent with better adsorption capacity to remove Cd 2+ in the solution.