Study On The Adsorption Performance Of MgO Nanopowders

Environmental pollution, especially water pollution, has increasingly seriouslythreatened human’s health and survival environment. Now, studying and developing newmaterials, new methods and new technologies to control water pollution has become thekey work of environmental protection fields. Due to their high adsorption capacity,environmental friendly, mild use condition, and low cost, nano-MgO powders presentunique advantages and application prospects in pollution abatement and environmentalprotection field. This paper systematically investigated the adsorption properties of theas-prapared nano-MgO powders towards organic dyes and heavy metal ions, in order tosupply reliable experiment practice and theoretical basis for the efficient treatment ofwater pollution.Nano-MgO powders were prepared by a simple sol-gel method, X-ray diffraction(XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET)surface area analysis were used to characterize the phase structure, morphology andspecific surface area of the as-prepared nano-MgO powders. In this paper, using theaqueous solution of methyl orange to simulate azo dye wastewater, the removal efficiencyof nano-MgO powders was examined through a series of batch adsorption experiments interms of different contact time, initial solution concentration and initial solution pH. Theadsorption rates and the adsorption capacities of nano-MgO towards methyl orange werevery high (qmax=195mg/g). The solution pH had a notable influence on the adsorptioncapacities of nano-MgO, and the adsorption capacities increased first, then decreasedgradually with the increase of pH value. Additionally, adsorption kinetics analysisindicated that the pseudo-second-order adsorption kinetics model could represent well theadsorption of nano-MgO towards methyl orange.Using the aqueous solution of Cd2+、Pb2+to simulate heavy metal wastewater, theremoval efficiency of nano-MgO powders towards Cd2+、Pb2+was investigated through a series of batch adsorption experiments in terms of different contact time, initial solutionconcentration and initial solution pH. The results showed that the adsorption rates werevery high, and equilibrium was obtained in about30min. The maximum adsorptioncapacities towards Cd2+、Pb2+calculated by Langmuir equation were2301mg/g and2612mg/g, respectively. In the binary system, a competitive adsorption was observed, showingpreference of adsorption in the order of Pb2+> Cd2+.Langmuir adsorption model could well represent the experimental data of Pb2+adsorption whether in the single or binary system, but it was just suitable for Cd2+adsorption in the single system. The initial solution pH had a notable influence on theadsorption of heavy metal ions from aqueous solutions, especially for Cd2+. Moreover, theadsorbed products were analyzed to discuss the adsorption action of MgO nanopowderstowards heavy metal ions. Interestingly, it was difficult to elute heavy metals from MgOnanopowders by water washing, even five times. The adsorption action towards heavymetal ions involves adsorption, cation exchange and precipitation of hydroxide.