| Heavy metal is one of the main water pollutants at present,which seriously threatens human health and environmental safety.Adsorption method is one of the effective methods to deal with heavy metal wastewater.The development of high efficiency,cheap and easily available adsorbent is one of the key problems in the study of heavy metal wastewater treatment.Based on the comprehensive characterization of natural zeolite,the potential of natural zeolite as an effective adsorption material for heavy metal wastewater was studied and the mechanism of adsorption process was studied by using basic research data.The related research in this paper laid the foundation for the application of natural zeolite in the treatment of heavy metal wastewater.The main means of characterization of the physicochemical properties of natural zeolite included scanning electron microscopy,fluorescent X-ray analysis,X-ray diffraction,particle surface Zeta potential measurement,particle size analysis and thermogravimetric analysis.On such basis,the factors affecting the adsorption of heavy metal wastewater by natural zeolite were studied,including the effect of the initial pH value of the adsorption system,the influence of adsorption time,the influence of the adsorbent dose and the influence of the initial concentration of heavy metals.In the analysis of the aboved factors,the interaction effects of coexisting heavy metal ions in the adsorption system were studied,including two-element,three-elementand four-element adsorption systems.Based on the basic experimental data obtained from research process,the adsorption mechanism was studied,including adsorption kinetics and adsorption isotherm.The experimental results of this paper showed that a.natural zeolite materials are composed of a variety of minerals,and the main minerals are Heulandite minerals,Clinoptilolite minerals,Quartz minerals,Silicon Oxide minerals and Nacrite-2M2 minerals.b.Under thesingle adsorption system,with the increase of zeolite dosage,the removal rate of heavy metal ions by natural zeolite gradually increased to saturation.For example,for zinc ions,when the initial concentration of zinc ions was 50mg/L,the adsorption removal rate increased from 8.216% to 76.322% with the rise of dosage of natural zeolite(from 1g/L to 10g/L)and the adsorption capacity of natural zeolite to zinc ions decreased from 8.216mg/g to 3.8161mg/g.Within a certain range,with the increase of pH value,the removal rate of heavy metal ions by natural zeolite increased.As for the copper ions,when the initial concentration was 33.3mg/L and the value of pH of solution was 2~7,the removal rate of natural zeolite to copper ions improved from 58.84% to 100%;the adsorption capacity of natural zeolite to copper ions increased from 4.9033mg/g to 8.3333mg/g.When the value of pH of solution was 7~11,the adsorption removal rate remained stable at 100% and the adsorption capacity of natural zeolite to copper ions kept at 8.3333mg/g.In a certain range,the adsorption removal rate had positive correlation to reaction time and the adsorption would tend to balance when the reaction time continues.c.There was competitive adsorption relationship between heavy metal ions under multiple adsorption system.For example,in the two-element adsorption system(copper and cadmium,copper and zinc,lead and zinc),the order of competitive adsorption was Cd>Cu,Cu>Zn and Pb>Zn respectivelyunder the influence of different dosage of zeolite and pH value of solution.In the three-element and four-element adsorption systems(lead and cadmium and copper,lead and copper and chromium,chromium and zinc and cadmium,lead and copper and zinc and cadmium),the competitive adsorption sequence was Pb>Cu>Cd,Pb>Cr>Cu,Cr>Cd>Zn and Pb>Cu>Cd>Zn respectively. |
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