N-cyanoguanidine modified-black peanut shell biochar: fabrication and its sorption for Cu(II) and Co(II) in a single and mixed solutions

Abstract

A N-cyanoguanidine (NCY)-modified black peanut shell biochar was fabricated via NCY to modify waste black peanut shell. X-ray diffraction, Fourier transform infrared, scanning electron microscope–energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were used to characterize its performance. Sorption experiments were made to perceive its sorption for Cu(II) and Co(II) and disclosed that Cu(II) had higher sorption selectivity in mixed binary and four-metal solution. Sorption kinetics showed that Cu(II) and Co(II) sorption fitted well with pseudo-1st–order kinetic and diffusion-chemisorption models. Sorption isotherms revealed that Langmuir model can better describe its sorption behavior for Cu(II) and Co(II) and its maximum Qm could reach up to 185.66 and 80.59 mg/g at 45 °C, respectively. Thermodynamic factors indicated that Cu(II) and Co(II) sorption on NCY-modified black peanut shell biochar was an endothermic and spontaneous manner. Both effective diffusion coefficients (kIp) and mass-transfer coefficients (DEx) proved that Cu(II) and Co(II) sorption comprised multiple-step paces. The major mechanism included electrostatic attraction, mass transfer, complex and chelation, and diffusion-chemisorption. This finding suggests that NCY-modified black peanut shell biochar can be potentially applied to dispose Cu(II) and Co(II)-bearing wastewater from spent new power batteries.