*2.3. Aqueous Batch Experiments*

The aqueous adsorption experiment was performed according to Bouhamed et al. [1]. To determine the adsorption isotherms of adsorbents, 10, 30, and 50 mg L−<sup>1</sup> of Ni, Cr, Cu, and Zn were tested by aqueous batch experiments. For Hg, 0.2, 0.6, and 1.0 mg L−<sup>1</sup> were tested. A serial dilution of standard solution was made to the intended concentrations; the pH value of the solution was controlled to be 5 ± 0.1 by using 0.01 M NaOH and 0.01 M HCl, which simulates the real contaminated sediment environment.

Batch adsorption experiments were carried out in a rotary shaker at 125 rpm using 50 mL capped glass bottles containing 20 mL of metal ion solutions and 25 mg of adsorbents, similar to our previous study [29]. The temperature was controlled at 30 ◦C and the contact time was up to 24 h to achieve an adsorption equilibrium. All the experimental operations were triplicated.

After shaking, samples were filtered with 0.45 μm filters and the supernatant was kept for metal analyses. For a long-time preservation, each sample of Ni, Cr, Cu, and Zn was preserved with 0.5% HNO3 and measured by flame atomic absorption spectroscopy (FAAS; Perkin Elmer AAnalyst 800, Waltham, MA, USA); each sample of Hg was preserved with 0.5% BrCl and estimated by cold vapor atomic fluorescence spectroscopy (CVAFS; Brooks Rand Automated Total Mercury System, Seattle, WA, USA). QA/QC were regularly checked by analyzing duplicate samples and quality control samples from each batch.
