It is vital to understand the adsorption mechanisms and identify the adsorption kinetics when applying an adsorbent to remove heavy metals from aqueous solution. A Pb(II) imprinted magnetic biosorbent (Pb(II)-IMB) was developed for the removal of Pb 2+ via lead ion imprinting technology and crosslinking reactions among chitosan (CTS), Serratia marcescens and Fe 3 O 4 . The effect of different parameters such as solution pH, adsorbent dosage, selectivity sorption and desorption were investigated on the absorption of lead ion by Pb(II)-IMB. The adsorbent was characterized by a Brunauer-Emmett Teller (BET) analysis, X-ray diffraction (XRD), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The adsorption kinetics, equilibrium and thermodynamics of Pb(II)-IMB for Pb(II) were studied. The results of the abovementioned analyses showed that the adsorption kinetic process fit well with the second-order equation. The adsorption isotherm process of Pb(II) on the Pb(II)-IMB was closely related to the Langmuir model. Thermodynamic studies suggested the spontaneous and endothermic nature of adsorption of Pb(II) by Pb(II)-IMB. The adsorption mechanism of Pb(II)-IMB was studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated that the nitrogen in the amino group and the oxygen in the hydroxyl group of Pb(II)-IMB were coordination atoms.

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A novel biological material with high adsorption capacity and good selectivity for Pb was synthesized. Response surface methodology was utilized for the optimization of the variables during the synthesis. The synthesized biosorbent was characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The optimized preparation condition for lead-ion-imprinted magnetic biosorbent (Pb(II)-IMB) was obtained (0.19 g chitosan (CTS), 0.43 g magnetic FeO and 2.11 mL/gCTS of epichlorohydrin). The highest value for the removal of lead ion was estimated to be 86.85%, with an absorption capacity of 69.48 mg/g. The characterization results indicated that Pb(II)-IMB was rich in adsorbable groups to adsorb metal ions. Because of the magnetic property of the synthesized products, it can be separated from the water easily. The relative selectivity coefficients of Pb(II)-IMB for Pb(II)/Cu(II), Pb(II)/Cd(II) and Pb(II)/Ni(II) were 2.32, 2.20 and 2.05 times higher than the non-imprinted magnetic biosorbent, respectively. Pb(II)-IMB could be reused at least five times with only ∼13% loss. These results suggested that Pb(II)-IMB was a new, efficient and low-cost material for removing Pb(II) from wastewater.

This study prepared an innovative 3-mercaptopropionic acid modified ZnSe/ZnS core/shell quantum dots (MPA-ZnSe/ZnS QDs), and established a rapid fluorescence method to detect the E. coli cells count by using MPA-ZnSe/ZnS QDs as fluorescence probe. The formulation variables and process were optimized using the response surface methodology (RSM). Fluorescence microscopy was used to obtain fluorescence microscope images of MPA-ZnSe/ZnS QDs that bind to bacteria. The fluorescence peak intensity increases with increasing cells count in the range of 101-108 CFU/mL. Compared with the traditional based on fluorescent detection methods, this method is more convenient and useful in the bacterial count determination.