In the present work, a facile two-step approach using polydopamine (pD) as a platform was developed to immobilize polyaspartate onto silica gels (SG) for enhancing the removal of methylene blue (MB) from aqueous solution. The chemical structures of the native and modified SG were characterized by FT-IR, SEM, and TGA. The adsorption behaviors of MB on SG, the pD-coated silica gels (SG-pD), and the polyaspartate-conjugated silica gels (SG-pA) were also compared. The results demonstrated that at pristine solution pH 6.2 SG-pA showed the highest adsorption capacity toward MB, the adsorption process on SG-pA was spontaneous, and the adsorption capacity of MB was reduced with temperature increasing. The kinetics studies indicated that SG-pA had the shortest equilibrium time of 540 min toward MB adsorption and the adsorption process followed the pseudo-second-order model. Furthermore, the data of the equilibrium isotherms for MB adsorption on SG-pA were in good agreement with the Langmuir isotherm model, and the maximum adsorption capacity for MB was 90.2 mg g(-1). In addition, SG-pA still displayed high adsorption capacity after three times of cyclic adsorption tests, implying that SG-pA was a potential reusable adsorbent for the removal of MB from effluent water relative to pristine silica gels. (C) 2015 Elsevier B.V. All rights reserved.

AbstractIn this study, tri-sodium citrate (CA), a chelating agent of low-cost and non-toxicity, was used together with epichlorohydrin (ECH) to cross-link chitosan (CTS) for enhancing the adsorption of Pb (II) and Cu (II) ions onto CTS. The chemical structure changes of the cross-linked CTS and metal ions-loaded absorbent were confirmed by thermogravimetric analysis, FTIR spectroscopy and X-ray diffraction. The effects of these factors, such as pH, temperature, contact time, and initial concentration of metal ions on the adsorption of Pb (II) and Cu (II) ions onto CTS–CA–ECH beads were investigated. The adsorption kinetics was evaluated utilizing pseudo-first-order and pseudo-second-order (PSO) models, the results indicated that the adsorption process fit well with the PSO kinetic model. Meanwhile, adsorption equilibrium isotherms were examined by Langmuir and Freundlich models, the results showed that the experimental data agreed well with Langmuir models and the maximum adsorption capacities were 121.95...

A simple, sensitive, and rapid chemiluminescence method combined with flow-injection analysis was developed for the determination of lisinopril. It was found that the chemiluminescence (CL) signal arising from the reaction of alkaline luminol with KMnO(4) could be significantly increased by addition of lisinopril in the presence of silver nanoparticles. The experimental parameters affecting the chemiluminescence reaction were carefully studied and the chemiluminescence reaction mechanism was briefly discussed. Under the selected conditions, the chemiluminescence intensity was proportional to the concentration of lisinopril ranging from 0.1 mg/L to 20.0 mg/L. The detection limit was 0.027 mg/L lisinopril and the relative standard deviation for 4.0 mg/L lisinopril solution was 1.9% over eleven repeated measurements. The proposed method was applied to the determination of lisinopril in tablets and spiked human urine samples.