Optical Chemosensor Based On HMS For The Detection Of Heavy Metal Ions In Aqueous Solution

With the rapid development of the global economy, the problem of water pollution is growing severely. Heavy metals pollution takes a fairly large proportion on water pollution. Heavy metals, which are a great hazard of pollutants, can accumulate chronically in vivo and is not easy to be degraded. The toxicity of heavy metals severely endanger the ecological environment and human health. Conventional detection methods for heavy metal ions, including atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), atomic fluorescence spectrometry (AFS) and inductively coupled plasma mass spectrometry (ICP-MS), etc, have disadvantages of sophisticated pretreatment procedures, time-consuming, expensive instruments and are difficult to meet the on-site requirement for rapid detection.In recent years, there has been growing interest in the development of optical chemosensor, as a new detection method for heavy metal ions, which has advantages of no pretreatment, low cost, high sensitivity and good selectivity. Mesoporous molecular sieves as the hosts of optical chemosensor have advantages of high surface areas, uniform pore size, surface with hydroxyl, simple synthesis and high thermal stability. The novel optical chemosensors based on luminescent molecules immobilizing on mesoporous molecular sieves have the advantages of both to meet the needs of practical detection for heavy metal ions.In this paper, a novel optical chemosensor (HMS-TMAC-PAR) for heavy metal ion detection had been prepared by immobilizing the luminescent molecule 4-(2-pyridylazo)resorcinol (PAR) on the functionalized HMS via N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAC). The successful fabrication of this material was confirmed by extensive characterizations using XRD, FT-IR, TG, elemental analysis, N2 physical adsorption and UV-vis, meanwhile its colorimetric properties, selectivity, sensitivity and reusability were also investigated. The results showed that HMS-TMAC-PAR responded selectively to heavy metal ions, such as Fe3+, Cd2+, Ni2+, Zn2+, Pb2+, Co2+, Hg2+and Cu2+with a color change from light yellow to orange or light purple in alkaline solutions, while under strongly acidic conditions HMS-TMAC-PAR responded selectively to Cu2+and showed a color change only for Cu2+. At pH 12, HMS-TMAC-PAR had a high sensitivity that maked it possible to detect Cu2+ in aqueous solution with a detection limit of 0.81 ppb and HMS-TMAC-PAR could be used repeatedly by treatment with a solution of EDTA.