| With the development of the industry, the phenomenon of heavy metal ions wa-ter pollution also exist widely. People have begun to pay more attention on the pol-lution of Ni2+ in water. The water pollution of Ni2+ is mainly derived from industry production. Ni2+ is one of the toxic ions which are difficultly removed from waste water by biodegradable methods. There are chemical, precipitation, oxidation and reduction, ion exchange, adsorption, reverse osmosis, electrolysis in the water treat-ment of Ni2+. To find a simple, stable and economical processing technology for processing waste water of Ni2+ is particularly urgent.The diatomite is from the ancient algae by diastrophism. It has a large surface area and strong adsorption capacity, it is a kind of rich mineral resources. It is widely used in the sewage treatment which is a good natural adsorbent with broad application in recent years.The paper introduces the source and hazards of Ni2+ from wastewater and the development of the technology of treatment firstly, then the paper describes the ap-plication of diatomite in the field of water treatment and the research of modification. Analysis the feasibility of modified diatomite in water treatment of Ni2+. To make up water based on the concentration of Ni2+ overweight wastewater which is discharged from a electroplating enterprise in Hebei province. To choose the best modification method from burning method, PAM method and calcium carbonate method by com-paring the effect of adsorbing Ni2+ from the three kinds of modified diatomite. To choose the optimum modification time, calcium carbonate and soil mass ratio, con-centration of sodium carbonate solution and modification temperature by the static experiment. To analysis the difference of the micro structure and composition of the diatomite between before modified and after by SEM and XRD.In static experiment, calcium carbonate modified diatomite adsorbs Ni2+ under different conditions:dosage of modified diatomite, water pH, reaction temperature and reaction time. To choose the best condition of static experiment by comparing the removal rate of Ni2+ in different conditions. The best adsorption condition of calcium carbonate modified diatomite is:add 1.0g calcium carbonate modified diatomite in 100mL water, the concentration of Ni2+ is 1.2mg/L, oscillating reaction 40min under 30℃. The removal rate of Ni2+ is 92.69%, the adsorption quantity of Ni2+ is 111.23ug/g. The treated water to concentrations of Ni2+ reached the requirements of "electroplating pollutants discharge standard" (GB21900-2008) the (≤0.1mg/L). To research on the dynamics of calcium carbonate modified diatomite, the results show that:calcium carbonate modified diatomite composite pseudo-second order model accurately. Particle diffusion and adsorption reaction are the steps which collectively control the reaction rate. The results of researching on adsorption isotherm show that: calcium carbonate modified diatomite to Ni2+ adsorption accords with Langmuir iso-therm and the Freundlich isotherm.In dynamic experiments, to test the Ni2+ concentration of outflow water change with time under the condition:different water inflow rate, thickness of adsorption layer, the concentration of inflow water and draw breakthrough curve. The optimum parameters of the dynamic adsorption experiments is that:water inflow rate is 6mL/min, the adsorption column diameter is 4cm, thickness of adsorption layer is 80cm, the Ni2+ concentration of inflow water is 1.2mg/L.In desorption experiment, the result show that:desorption rate can reach more than 95% by using the different concentration of hydrochloric acid to desorption, but the adsorption rate of modified diatomite which has been desorbed is low, So the modified diatomite is not recommended for desorption and recycling.The effect of waste water containing Ni2+ adsorption of calcium carbonate mod-ified diatomite is obvious based on the analysis of all experimental conclusion and mechanism. The calcium carbonate modified diatomite which has a broad prospects is used in the aspect of water environment pollution treatment significantly. |
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