Abstract
In this study, a surface chemical-modified rice husk biochar with abundant amino groups and disulfide bonds for the removal of cadmium was prepared using cystamine dihydrochloride as a modification ligand and glutaraldehyde as a crosslinker. The biochars were characterized by Fourier transform infrared spectrometry (FTIR), elemental analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetry analysis (TGA), and nitrogen sorption (BET) before and after modification. The adsorption properties of the modified biochars for Cd (II) were investigated in detail via adsorption isotherm models, adsorption kinetics models, and selective adsorption experiments. The surfaces of the cystamine-modified biochars with granular nanopolymers of sufficient functional groups of primary amine and disulfide linkage rendered the biochar surface more conducive to electrostatic attraction and surface complexation. The theoretical maximum adsorption capacity of the modified biochars (81.02 mg g−1) was almost 10-fold greater than that of the raw biochars (8.347 mg g−1) for Cd (II). Besides, the cystamine-modified biochars had a better affinity for Cd (II) compared to other heavy metals (Zn, As, Cd, Co, Ni, Cr), showing six-fold greater affinity for Cd (II) than Zn2+. The results of this study indicate that the modification of biochars derived from rice husks shows great potential in the removal of Cd (II) from contaminated water.
Highlights
Environmental pollution and food safety are two of the most important issues of our time
Cadmium is not an essential nutrient element for the human body, but is an environmental pollutant that is mainly generated from industrial effluent and sludge, such as that associated with zinc mining, sewage treatment, and electroplating
FTCIhRanogf eRsaiwn tahnedfuCnycsttiaomnainl ge-rMouopdsifoifedbiBociohcahrsarbsefore and after modification were analyzed by Fourier transform infrared spectroscopy (FTIR) (Figure 2)
Summary
Environmental pollution and food safety are two of the most important issues of our time. Among all types of pollutants reported, heavy metals are considered to present the greatest risk to food safety in China [2]. According to a recent official nationwide survey in China, 39 of 55 sewage irrigation areas were contaminated by cadmium (Cd), arsenic (As), and polycyclic aromatic hydrocarbons [4]. The World Health Organization (WHO) has listed Cd as an important food contaminant for research, the International Agency for Research on Cancer (IARC) has classified Cd as a human carcinogen that causes serious health damage to humans, and the American Toxicology and Disease Registry (ATSDR) has listed Cd as the substance that is seventh most harmful to human health. It is important to develop methods for the removal of cadmium from the environment
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