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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&minus, 1) was almost 10-fold greater than that of the raw biochars (8.347 mg g&minus, 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.

We report the use of biochar and Fe3O4 nanoparticles as co-stabilizers for oil-in-water (o/w) Pickering emulsion. The emulsion is subsequently used to prepare magnetic tetracycline-imprinted biochar composite microspheres (MMIPMs) with good uniformity and high selectivity. The MMIPMs were characterized by scanning electron microscopy (SEM), Brunner-Emmet-Teller (BET) measurements, Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermogravimetry analysis (TGA). The adsorption properties of tetracycline to the MMIPMs were investigated using different adsorption experiments including adsorption kinetic experiment, equilibrium binding experiment, selectivity evaluation and competitive adsorption tests. The theoretical maximum adsorption capacity of the MMIPMs (15.45 mg g&minus, 1) was greater than that of the raw biochar (2.10 mg g&minus, 1) and non-imprinted biochar composite microspheres (3.39 mg g&minus, 1) for tetracycline. Further, the MMIPMs were used as adsorbent for magnetic solid phase extraction (SPE) for the extraction of tetracycline present in drinking water, milk, fish and chicken samples. Under optimal conditions, the results showed good recovery yield ranging from 88.41% to 106.29% with a relative standard deviation (RSD) ranging from 0.35% to 6.83%, respectively.