| Heavy metal pollution is an urgent problem to be solved in environmental pollution.Heavy metal wastewater comes from chemical industry,paper making,metallurgy,livestock and poultry breeding and other aspects.Heavy metal composition is also complex and diverse.Cadmium pollution is particularly prominent.Cadmium can not only migrate and transform in water,but also have adverse effects on aquatic organisms.It can enrich in human body through biological chains,which will affect human survival.Health is also a potential threat.How to develop effective removal technology of cadmium in water has become a hot issue in water pollution control.As a natural mineral,zeolite is abundant in China and has been widely concerned as an adsorbent for water pollution treatment.In this paper,application of sodium hydroxide to modification of natural zeolite,p H,zeolite addition amount,adsorption time,pollution and other conditions on both the effect of cadmium in the wastewater,adsorption by adsorption kinetics and adsorption thermodynamic discussion to cadmium ions in sodium hydroxide modified zeolite adsorption mechanism,to improve the efficiency of heavy metal waste water purification,explore the modified zeolite containing heavy metals cadmium wastewater treatment to provide further theoretical support,providing a new method for developing new type of heavy metal sewage purifying agent.The main conclusions are as follows:(1)By scanning electron microscopy(SEM)of natural and modified zeolite morphology observation,and energy spectrum analysis of the two elements,you can see Na OH appear similar to the coral reefs of the modified zeolite surface structure,surface roughness,channel structure significantly increased,deepen,and hole diameter increasing the specific surface area has increased considerably.Energy spectrum analysis showed that the si-al ratio of modified zeolite decreased significantly,which proved that Na OH solution as modification method could effectively remove the silicon elements in zeolite structure,reduce the si-al ratio of zeolite,and improve the adsorption performance of zeolite.(2)Under the principle of control variables,with the increase of zeolite addition amount,the adsorption of natural zeolite and modified zeolite first increased and then reached a steady state,but the adsorption amount continued to decrease;With the gradual increase of the adsorption time,the adsorption rate and the adsorption capacity had similar trends,which gradually increased and then remained stable at 6h and 2h respectively.As the initial Ph value of the solution increased,the adsorption rate and adsorption capacity first increased and then tended to be stable.With the increase of the initial concentration of the solution,the adsorption capacity of natural zeolite and modified zeolite gradually increased,and then reached the adsorption saturation,no longer increased,and tended to be stable.The adsorption level of Na OH modified zeolite was higher than that of natural zeolite.(3)The Langmuir adsorption isotherm model can better describe the adsorption process of the two than the Freundlich adsorption isotherm model.At different temperature levels,the increase of temperature can promote the adsorption behavior.According to the fitting of adsorption kinetic equation,the adsorption behavior of natural zeolite and modified zeolite conforms to the quasi-second-order adsorption kinetics,indicating that they belong to chemical adsorption.The particle internal diffusion model was fitted in a piecewise form,indicating that there were several rate-controlling steps in the process of zeolite adsorption of cadmium ions in water body,in which the initial stage of adsorption was liquid film diffusion process,and the later stage was the process of adsorption ions diffusing internally through adsorption pore channels.The fitting parameters of adsorption thermodynamics show that natural zeolite and modified zeolite are spontaneous chemical adsorption reactions.(4)It can be concluded from the research results that Na OH solution is more successful in the modification of natural zeolite and effectively increases the adsorption capacity of zeolite.In addition,compared with natural zeolite,Na OH modified zeolite can purify the wastewater containing cadmium faster in the wastewater with high cadmium pollution concentration and low Ph value. |
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