A new chromium(III)-imprinted azodicarbonamide-functionalized attapulgite sorbent was synthesized by a surface imprinting technique and was employed as a selective solid-phase extraction material for speciation analysis of chromium(III) in environmental water samples prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). The experimental conditions for the effective adsorption of Cr(III) were optimized with respect to different experimental parameters using static and dynamic procedures in detail. Compared with non-imprinted sorbent particles, the ion-imprinted sorbents had higher selectivity and adsorption capacity for Cr(III). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbents for Cr(III) was 69.75 and 21.06 mg g⁻¹, respectively. The relative selectivity factor values (α_r) of Cr(III)/Pb(II), Cr(III)/Cu(II), Cr(III)/Ni(II), Cr(III)/Sb(III), Cr(III)/As(III) and Cr(III)/Fe(III) were 55.46, 49.52, 44.53, 49.24, 41.77, and 26.63 respectively, which were greater than 1. The imprinted attapulgite sorbent offered fast kinetics for the adsorption and desorption of Cr(III). Under the optimized conditions (pH – 5.0, mass – 30 mg, shaking time – 20 min), a detection limit of 0.25 ng mL⁻¹ with a relative standard deviation (RSD) of 2.4% for Cr(III) was obtained. The method has been validated by analyzing certified reference materials and successfully applied to the determination of trace Cr(III) in environmental samples.

A novel hydrophobic and cationic cyclodextrin-based acrylamide flocculant (AM-β-CD-DMDAAC) was prepared by chemical oxidative polymerization to adsorb water-soluble dyes in dye wastewater. Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope and thermogravimetric (TG) measurements results demonstrated that the AM-β-CD-DMDAAC was successfully synthesized. The effects of pH, contact time, initial dye concentration, temperature and adsorbent dose on dye removal efficiency for AM-β-CD-DMDAAC flocculants were investigated. The kinetic data were found to follow the pseudo-second-order kinetic model. The equilibrium adsorption data were fitted to the Langmuir isotherm model, with the maximum adsorption capacity of 147.1 mg g⁻¹. The adsorbent retained about 60% of the adsorption efficiency after three adsorption/desorption cycles, which implied a promising application as the dye adsorbent.

Even the lowest concentration level of lead (Pb) in the human body is dangerous to health due to its bioaccumulation and high toxicity. Therefore, it is very important to develop selective and fast adsorption methods for the removal of Pb(II) from various samples. In this paper, a new Pb(II) ion-imprinted polymer (Pb(II)-IIP) was prepared with surface imprinting technology by using lead nitrate as a template, for the solid-phase extraction of trace Pb(II) ions in environmental water samples. The imprinted polymer was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and N₂ adsorption–desorption isotherms. The separation/pre-concentration conditions for Pb(II) were investigated, including the effects of pH, shaking time, sample flow rate, elution conditions and interfering ions. Compared with non-imprinted particles, the ion-imprinted polymer had a higher selectivity and adsorption capacity for Pb(II). The pseudo-second-order kinetics model and Langmuir isotherm model fitted well with the adsorption data. The relative selectivity factor values (α_r) of Pb(II)/Zn(II), Pb(II)/Ni(II), Pb(II)/Co(II) and Pb(II)/Cu(II) were 168.20, 192.71, 126.13 and 229.39, respectively, which were all much greater than 1. The prepared Pb(II)-imprinted polymer was shown to be promising for the separation/pre-concentration of trace Pb(II) from natural water samples. The adsorption and desorption mechanisms were also proposed.

Multiwalled carbon nanotubes modified with 4-Aminoazobenzene was prepared and applied to the separation, preconcentration and determination of Pb(II) in aqueous solutions by inductively coupled plasma optical emission spectrometry. Characterisation of the surface modification was performed on the basis of transmission electron microscopy, Fourier transform infrared spectra and elemental analysis. The effects of pH, the sample flow rate and volume, the elution condition and the interfering ions were examined using batch and column procedures in detail. Under the optimised conditions (pH 5.0, flow rate 2.0 mL min⁻¹), Pb(II) retained on the column can be quantitatively eluted by 2.0 mL 0.1 mol L⁻¹ HCl. An enrichment factor of 150 was accomplished. Common interfering ions did not interfere in both the separation and determination. The maximum adsorption capacity of the adsorbent at optimum conditions was found to be 46.8 mg g⁻¹. The detection limit (3σ) was 0.28 μg L⁻¹, and the relative standard deviation (RSD) was 2.1% (n = 11). The method was validated using certified reference materials, and has been applied for the determination of trace Pb(II) with satisfactory results.