| Heavy metals can persist in the environment water for a long time,which pose a great threat to human health and ecosystem safety.The development of nanotechnology provides a great opportunity for the removal of heavy metals in water Among various nanomaterials,resin-supported metal oxide nanomaterials are favored for their excellent properties such as high mechanical strength,no agglomeration during water treatment and easy recovery after use.However,some resin-supported metal oxide nanomaterials have low adsorption capacity for heavy metals.Therefore,it is of great significance to enhance their adsorption capacity by functional modification.The resin-supported metal oxide nanomaterials may release nanoparticles(NPs)into the water due to the fall-off of the NPs during the pollutant removal processes,which could weaken the adsorption performance of the materials and cause secondary pollution.Therefore,studying the release of NPs from resin-supported metal oxide nanomaterials in water will provide key basic data for evaluating the stability and safety of the materials.Aiming at the above-mentioned problems,this paper carried out three aspects of researchFirstly,resin-supported Fe2O3 NMs(HFO-201)was modified by humic acid(HA),and the produced HA-HFO-201 was utilized for removing heavy metal ions from water.Physical and chemical characterization of HA-HFO-201 was carried out by means of scanning electron microscopy-energy spectrum(SEM-EDS),transmission electron microscope-energy spectrum(TEM-EDS),N2 adsorption-desorption isotherm analysis.The results showed that HA-HFO-201 was a microsphere with a diameter of 0.6-0.8 mm,mesoporous structure,large specific surface area and pore volume,and Fe2O3 NPs was evenly distributed in the resin.The adsorption kinetics of heavy metal ions(Cu(?),Cd(?)and Pb(?))by HA-HFO-201 followed pseudo-second-order kinetic equation.The modification of HA markedly enhanced the adsorption capacity of heavy metal ions.For Cu(?),Cd(?)and Pb(?),the maximum adsorption capacities of HA-HFO-201 were 88.96,65.67 and 101.4 mg/g respectively,while the maximum adsorption capacities of HFO-201 were 2.41,3.50 and 2.48 mg/g,respectively.HA and solution pH have no remarkable influence on the adsorption of heavy metal ions to HA-HFO-201.HA-HFO-201 can selectively adsorb Cu(?),Cd(?)and Pb(?)even in the coexistence of Ca(?)at the concentration of 50 times of the metals.The adsorbed Cu(?),Cd(?)and Pb(?)on HA-HFO-201 could be eluted and recovered by Na2EDTA solution,while the HA-HFO-201 was regenerated simultaneously with good performance in adsorption capability after recycling 5 timesSecondly,resin-supported ZrO2 NMs(HZO-201)was modified by HA,and the produced HA-HZO-201 was evaluated in view of its capability for removal of Cr(?)and Hg(?),in both batch and packed column treatment mode,from CODCr testing wastewater.The results showed that the pH no remarkable influence on Hg(?)removal,while the removal ability of Cr(?)is strongly dependent on the solution pH The NaCl concentration in solution has no obvious effect on Cr(?)and Hg(?)removal.Using three HA-HZO-201 packed columns in series,when 70 bed volume of water containing 200 mg/L Cr(?)and 1000 mg/L Hg(?)was treated,the Cr(?)and Hg(?)in the treated water were below their wastewater discharge limits(1.5 mg/L Cr(?),0.05 mg/L Hg(?)).By using 0.1 mol/L HNO3 and 0.5 mol/L thiourea solution to elute the adsorbed Cr(?)and Hg(?),respectively,the used HA-HZO-201 can be regenerated for reuse,and the recovery of Cr(?)and Hg(?)can be realized at the same time.This treatment process is environmentally friendly,as no waste residue is generatedFinally,the amount and species of Zr released from the resin-supported ZrO2 NMs(HZO-201)was evaluated,during the treatment of electroplating wastewater About 5 g of the HZO-201,a porous sphere(0.8 mm in diameter)loaded with ZrO2 NPs,were packed into a glass column(130 mm in length and 20 mm in diameter)to treat wastewater at flow rate of 25 mL/h.The release of Zr occurred mainly in the initial stages of water treatment,decreased with the increase of treatment volume,and approached an equilibrium value of approximately 3.79?g/L at the treatment volumes of about 800 bed volume.The released amount of Zr under acidic and alkaline conditions was markedly higher than that under neutral conditions,while the presence of HA significantly inhibited the release of Zr.Further,Zr ions and ZrO2 NPs were separated by ultrafiltration,and analyzed by ICP-MS and TEM-EDS,respectively.It was found that the released of Zr were mainly in the form of ZrO2 NPs.These results suggested that metal oxide NPs may be released from resin-supported metal oxide nanomaterials during water treatment,which may affect the long-term stability of the materials and environmental safety. |
PDF Full Text Request