Creation of Hollow Calcite Single Crystals with CQDs: Synthesis, Characterization, and Fast and Efficient Decontamination of Cd(II)

Abstract

In this work, carbon quantum dots were first prepared through one-pot hydrothermal route of the propyl aldehyde and sodium hydroxide via an aldol condensation reaction, and a novel solid-phase extraction adsorbent of hollow calcite single crystals was prepared via the precipitation of metal nitrates by the CO2 diffusion method in the presence of CQDs and further applied for excessive Cd(II) ions removal from water. The spectra and morphologies of the etched calcite were investigated by X-ray diffraction, Fourier transform infrared spectrometry, Scanning electron microscope, and Transmission electron microscopy. The results show that the CQDs etching technique successfully furnish a strategy for manufacturing interface defects onto the calcite crystal. Bath studies were done to evaluate the effects of the major parameters onto Cd(II) adsorption by the etched calcite, such as pH, contact time, and initial Cd(II) concentration. The Cd(II) adsorption onto the new adsorbent could reach a maximum adsorption amount of 66.68 mg/g at 120 min due to the abundant exterior adsorption sites on the adsorbent. The adsorption kinetics and adsorption isotherms of Cd(II) on the etched calcite were also investigated. The experimental datum showed that the adsorption kinetics and isotherms of Cd(II) on the etched calcite were well-fitted by the pseudo-second-order kinetic model and the Freundlich isotherm model respectively. The adsorption mechanisms could be primarily explained as the formation of Cd(OH)2 and CaxCd1−xCO3 solid solution on the adsorbent surface with the help of X-ray photoelectron spectroscopy.

Pristine and Magnetic Kenaf Fiber Biochar for Cd2+ Adsorption from Aqueous Solution

“…Meanwhile, Figure 10d shows that the Cd 3d3/2 core-level spectrum has two peak components with binding energies of about 413.5 eV, 406 eV, and 402 eV, which can be attributed to Cd-O and Cd (OH) 2 species, respectively. The findings show that Cd(II) deposition and chelation played a significant role in the adsorption mechanism [82].…”

Electrochemical method for isolation of chitinous 3D scaffolds from cultivated Aplysina aerophoba marine demosponge and its biomimetic application

“…Heavy metals present in water resources pose a high risk of hazard for human health as well as the environment. It is well recognized that calcite has a great ability to adsorb heavy metal ions [104][105][106][107][108]. Indeed, natural calcite as limestone [109] or in the form of waste chicken eggshells [110] has been used for heavy metal removal.…”

The Characteristics of Limestone and Anthracite Coal as Filter Media in Treating Pollutants from Groundwater

“…A positive charged surface can create adsorption interactions, such as hydrogen bonding, chelation and electrostatic interaction. Thus, this particular characteristic in limestone is suitable to immobilise charge ontaminants during adsorption [18]. The presence of CaCO 3 in limestone increases the removal of Fe and Mn through metal precipitation [10].…”