Preparation of a Novel Millet Straw Biochar-Bentonite Composite and Its Adsorption Property of Hg2+ in Aqueous Solution

Abstract

The remediation of mercury (Hg) contaminated soil and water requires the continuous development of efficient pollutant removal technologies. To solve this problem, a biochar–bentonite composite (CB) was prepared from local millet straw and bentonite using the solution intercalation-composite heating method, and its physical and chemical properties and micromorphology were then studied. The prepared CB and MB (modified biochar) had a maximum adsorption capacity for Hg2+ of 11.722 and 9.152 mg·g−1, respectively, far exceeding the corresponding adsorption value of biochar and bentonite (6.541 and 2.013 mg·g−1, respectively).The adsorption of Hg2+ on the CB was characterized using a kinetic model and an isothermal adsorption line, which revealed that the pseudo-second-order kinetic model and Langmuir isothermal model well represented the adsorption of Hg2+ on the CB, indicating that the adsorption was mainly chemical adsorption of the monolayer. Thermodynamic experiments confirmed that the adsorption process of Hg2+ by the CB was spontaneous and endothermic. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and a thermogravimetric analysis (TGA) showed that after Hg2+ was adsorbed by CB, functional groups, such as the –OH group (or C=O, COO–, C=C) on the CB, induced complexation between Hg and –O–, and part of Hg (ii) was reduced Hg (i), resulting in the formation of single or double tooth complexes of Hg–O– (or Hg–O–Hg). Therefore, the prepared composite (CB) showed potential application as an excellent adsorbent for removing heavy metal Hg2+ from polluted water compared with using any one material alone.

Recovery of Waste Polyurethane from E-Waste. Part II. Investigation of the Adsorption Potential for Wastewater Treatment

“…Considering the results of the equilibrium tests (Figure 1 and Table 3), for all target contaminants, the equilibrium of adsorption was reached more quickly with AC, so that the test was stopped earlier than for reactors with PUF, since no significant changes in liquid concentration were detectable. Compared to PUF, the much shorter t eq found for AC is reasonably a consequence of its high specific surface area [14] and of the hydrophobic nature of polyurethane, which could make adsorption slower [32]. The pollutants reached the adsorption equilibrium on AC rather quickly (30-35 min), while waste PUF required much longer times: 60 min for methylene blue, and 135-140 min for phenol and mercury.…”

Mercury Removal from Contaminated Water by Wood-Based Biochar Depends on Natural Organic Matter and Ionic Composition

“…To treat such contaminated waters, novel materials are being developed, including polymers, 8 functionalized clays, 9 carbonaceous materials, 10 and composites thereof. 11 Although these sorbents are widely investigated, their large-scale application may be economically challenging in low-income countries. The use of a low-cost carbonaceous sorbent such as biochar may provide an alternative to treat Hg(II)-contaminated waters.…”

“…For example, effluents from many gold mining areas, coal power plants, biomedical, paper and pulp industries, and even groundwater in some historically contaminated sites still continue to report high Hg­(II) concentrations ranging between 0.75 and 10 μM. To treat such contaminated waters, novel materials are being developed, including polymers, functionalized clays, carbonaceous materials, and composites thereof . Although these sorbents are widely investigated, their large-scale application may be economically challenging in low-income countries.…”

Carboxin and Diuron Adsorption Mechanism on Sunflower Husks Biochar and Goethite in the Single/Mixed Pesticide Solutions

“…and organic compounds [ 13 ]. Dolomite with addition of tea waste [ 14 ] and bentonite with addition of biochar [ 15 ] are examples of such materials. Development of mixed adsorbents is a very ecological trend.…”

“…Mixed adsorbents may be used in wastewater treatment and soil remediation technologies [ 19 , 20 ]. Usually, they are obtained in two steps: mixing mineral with biomass and pyrolysis of prepared mixture at high temperature [ 15 ].…”