Self-Templated Formation Of Hollow Metal Sulfide Nanomaterials And Their Adsorption Properties For Heavy Metal Ions In Water

The continuous growth of modern industrial activities has been accompanied by the generous release of effluents rich in heavy metal ions,which seriously pollutes the ecological environment and poses a serious threat to human health.Therefore,the abatement of heavy metal ions has become an essential prophylactic measure to protect human health,ecosystems,and food security.Since several conventional adsorbents are difficult to remove heavy metal ions with trace levels,it is highly desirable to develop more efficient and economical adsorbents that can achieve high-efficiency trace removal of heavy metal contamination.Fabrication of new environmentally friendly materials with large specific surface area and flexible surface active sites is an effective way for water body repair.Based on the above problems,two different hollow metal sulfide nanomaterials were prepared in this work.The adsorption properties and adsorption mechanism of two nanomaterials on typical heavy metal ions in aqueous solution were investigated.The main contents are as follows:?1?A facile self-templated strategy for the synthesis of novel hollow nanoparticles from Ni₂S was adopted.The nickel precursor of the quadrangular nanoprism was firstly synthesized as the self-sacrificing template.Afterwards,thioacetamide?TAA?was added to consume these Ni precursors during the reflow process for the simultaneous growth of a layer of Ni₂S shell around them.The resultant Ni₂S hollow nanoparticles manifested high adsorption performance towards t Pb²⁺ions in aqueous solution.Ni₂S hollow nanoparticles suggested an adsorption capacity of up to 695.47 mg g^-1.And Ni₂S hollow nanoparticles could rapidly reduce the Pb²⁺ion concentration from the ppm levels to a trace levels of3 ppb.The sorption kinetics for Pb²⁺followed a pseudo-second-order model suggesting a chemisorption with the adsorption mechanism via M-S bonding.Sorption isotherm for Pb²⁺was in good agreement with the Langmuir model,and showed a monolayer adsorption.A remarkable selectivity for Pb²⁺was achieved in the presence of coexisting cations and anions.There was a high removal rate of Pb²⁺ions over an initial pH ranging from 3 to 7.?2?Polyhedral CoS hollow nanocage material was successfully synthesized using ZIF-67 as the sacrificial template,which demonstrated extremely efficient removal of heavy metal ions such as Cu²⁺,Zn²⁺,Pb²⁺,Ag⁺and Cd²⁺.The CoS hollow nanocage material displayed a selectivity order of Ni²⁺<<Zn²⁺,Cd²⁺<Pb²⁺,Cu²⁺,Ag⁺for six different heavy metal ions.The enormous capacities for Ag⁺(2147.944 mg g^-1)and Pb²⁺(813.808 mg g^-1)demonstrated high distribution coefficients?K_d?of 10⁷ mL g^-1.CoS hollow nanocage material presented promising property for removal of heavy metal ions.Sorption isotherm for Cu²⁺,Zn²⁺,Pb²⁺,Ag⁺and Cd²⁺was consistent with the Langmuir model,and showed a monolayer adsorption.And the CoS hollow nanocage material can rapidly reduce the Ag⁺ion concentration from the ppm levels to a trace levels of 1 ppb.The sorption kinetics for Cu²⁺,Zn²⁺,Pb²⁺,Ag⁺and Cd²⁺followed a pseudo-second-order model,and revealed a chemisorption with the adsorption mechanism via M-S bonding.In addition,the Ag⁺removal efficiency exceeded99.9%over an initial pH ranging from 3 to 7.