Amorphous MnO₂ Modified Biochar Derived from Aerobically Composted Swine Manure for Adsorption of Pb(II) and Cd(II)

Abstract

This study reports creative preparation of MnO 2 -biochar (MBR) via MnO 2 modification of biochar (BR) derived from aerobically composted swine manure. SEM coupled with EDX analyzer, TEM, XRD, BET, and FT-IR were employed to examine the surface properties and pore structures of MBR and BR. Adsorption experiments of Pb(II) and Cd(II) including isotherms, kinetics, and thermodynamics as well as the influence of pH on zeta-potential were also investigated. The results indicated that MBR showed rougher and larger surface area and pore volume than BR. In batch adsorption, MBR showed superior adsorption performance (maximum capacity for Pb 268.0 mg/g and Cd 45.8 mg/g) to BR (Pb 127.75 and Cd 14.41 mg/g). The adsorption process was pH-dependent, and the removal efficiency reached its maximum at 0.2 g/L dosage of MBR, after which it declined. Finally, X-ray photoelectron spectrometer (XPS) studies indicated the oxidative Mn 4+ on MBR, and suggested that apart from electrostatic attachment, specific adsorption (i.e., Pb/Cd−O or hydroxyl binding) and ion exchange were the removal mechanisms of metal ions. Therefore, this modification method toward BR was promising for wastewater treatment of heavy metal pollution.

Preparation and Pb (II) adsorption in aqueous of 2D/2D g‐C3N4/MnO2 composite

“…However, the FT‐IR spectra of g‐C 3 N 4 /MnO 2 composite exhibited different characteristics. Two absorption bands of g‐C 3 N 4 /MnO 2 observed at 450 and 511 cm −1 corresponded to the Mn−O bond . Additionally, a broader band at about 3401 cm −1 , which belonged to the associated hydroxyl groups on the surface of MnO 2 , was found in the spectrum of g‐C 3 N 4 /MnO 2 composite.…”

“…The FT‐IR spectra of g‐C 3 N 4 and g‐C 3 N 4 /MnO 2 were shown in Figure . As for the single g‐C 3 N 4 , several bands at about 3000–3500 cm −1 can be ascribed to the combined effects of the stretching vibration of amino groups (‐NH 2 or ‐NH‐) and a small amount of ‐OH . The characteristic band of C=N appeared at 1630 cm −1 , and the peaks at 1469, 1327 and 1241 cm −1 responded to the typical stretching of C‐N .…”

“…Additionally, the Q cal values confirmed by using the pseudo‐second‐order model were distinctly close to the experimental Q exp (Table ). These results illustrated that the pseudo‐second‐order model could well fit the adsorption kinetic data of Pb (II), which indicated that the adsorption of Pb (II) was controlled by chemical sorption …”

“…Finally, the black composite was washed by distilled water and ethanol three times, and then dried at 323 K for 24 hr. The synthetic mechanism of MnO 2 nanoparticles was expressed as follows: …”

“…The harmful impacts of heavy metals in the environment are mainly attributed to the fact that they cannot be degraded biologically towards animals, plants and human beings . Many technologies, such as membrane filtration, electrolysis, ion‐exchange, adsorption and precipitation, have been studied for the treatment of heavy metals in effluents. Specially, adsorption is considered to be one of the most effective methods for removal of contaminants .…”