Study On The Adsorption Of Functionalized Mesoporous Material MCM-41 Toward Copper Ion In The Wastewater

The removal and selective recovery of heavy metal from industrial wastewater are an inherent requirement of circular economy. Currently, numerous remedies are adopted to dispose effluent containing heavy metal ions, and adsorption process is widely used due to low cost, facile operation and high retention ratio. The order mesoporous sieve MCM-41 is one of novel adsorbents with unique traits such as large specific surface area (700-1500m²/g), regular architecture and open framework, well-defined and controllable pore size (2-50nm),well-modified surface properties and flexible attach fraction. So it has obvious advantages over conventional adsorbents in the following aspects: (1) MCM-41 is superior to traditional adsorbents in adsorption capacity, saturation time, selectivity; (2) MCM-41 can be easily functionalized with various organic compound to yield complexation between grafted ligand and metal ions, which can enhance the adsorption capacity for target heavy metal to attain optimum uptake.In the first stage of this paper, pure MCM-41 and amino-modified MCM-41 were synthesized using one-pot method under microwave. The two solids were characterized by X-ray diffraction, FT-IR spectroscopy, nitrogen gas sorption- desorption and were used for adsorption of Cu²⁺ in waste water. The adsorption behavior and adsorption kinetic properties together with regeneration capacity and enrichment capacity for trace metal of the two samples were examined in detail, respectively. The results indicated that the adsorption behaviors of Cu²⁺onto the two adsorbents all fitted to the Langmuir isotherm equation, the maximum adsorption capacity of the amino modified silica was 24.94mg/g, while that of pure silica was 14.9mg/g. Compared with the half-life periods of pure silica(2.13min), the half-life periods of amino modified silica was a little longer(2.18min); Furthermore, the two adsorbents could be utilized to preconcentrate the trace metal in the medium, the adsorption capacity of NH₂-MCM-41 could be easily restored.In the second stage, The modified MCM-41 with three kinds of thiol group contents were synthesized using one-pot method under microwave, the SH-3-MCM-41(the molar fractions of–SH group was 40%) surprisingly preserved a high order in the mesoscopic architecture confirmed by structural characterization. As thiol group concentration increased from 20% to 40%, there was a noticeable decrease in specific surface area, pore volume and pore size of the three materials. Cu(â…¡) adsorption experiment data revealed that SH-3-MCM-41 possessed better adsorption property than the counterparts with maximum adsorption capacity of 27.10mg/L and half-life period of 2.44min. the pH of solution had a negative effect on the adsorption of copper on SH-3-MCM-41, the competitive adsorption experiments showed that the presence of other cations (Pb²⁺,Zn²⁺,Co²⁺)in the solution had little effect on the adsorption of Cu²⁺ on SH-3-MCM-41, SH-3-MCM-41 could be employed to preconcentrate the trace metal in the medium and could be regenerated five times with considerable reloading capacities.In the third stage, the EDTA-MCM-41 was successfully synthesized using NH₂ -MCM-41 and EDTA as starting materials ,The characterization results presented that the cheap and excellent chelate (EDTA) was anchored to the framework of MCM-41 the stability of the novel material in solutions of different pH was determined by elemental analysis. Then the solid was employed as a Cu(â…¡) adsorbent from simulative wastewater. The thermodynamic and kinetic properties together with regeneration capacity and enrichment capacity for trace metal of the prepared sample has been investigated in detail, the effect of presence of different anions in the medium on Cu(â…¡) adsorption amount has been demonstrated, too. The adsorption experiment data exhibited that the adsorption behavior of EDTA-MCM-41 fitted well to the Langmuir model at 298K which Q0 was 33.22mg/g and the half-life period of extraction was2.04min. The EDTA-MCM-41 possessed a dramatic affinity for trace copper ions in solution. The high Cu(â…¡) uptake efficiency of 90.9% was maintained after 5 loading and elution cycles. The efficiency of the EDTA-MCM-41 to bind Cu(â…¡)ions was slightly influenced by the presence of different anions from solution in the order of NO3-=CO32-