Study On Water Quality Improver Prepared By Oyster Shell

Oyster shell, which has special physical structure and good adsorption capacityof pollutants in waters, can be used to prepare water quality improver. This papermade use of special structure and properties of oyster shell powder to explore itsadsorption property of adsorbing5kinds of heavy mental ions Cu²⁺、Zn²⁺、Pb²⁺、Cd²⁺、Cr（Ⅵ） and studied adsorption effect of pollutant such as Cd²⁺onto oyster shellpowder which modified by different method. On this basis, compound water qualityimprover focus on adsorbing heavy mental ions was prepared. It confirmed byexperiments that the compound water quality improver had good absorption capacityof adsorbing main pollutant in water and could be used to improve breeding water.1) This paper studied the adsorption effect of oyster shell powder at the differentoyster shell dosage, adsorption temperature, pH value, adsorption time and initialconcentration of heavy metal ions on adsorbing Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Cr（Ⅵ）,analysed its adsorption kinetics, adsorption isotherms and SEM pictures. Theexperiment indicated that the most appropriate adsorption condition is as follows：atroom temperature, dosage is1g/L, pH value is5.5, and adsorption time is24h, theremoval ratio of1mg/L Cu²⁺、Zn²⁺、Pb²⁺、Cd²⁺、Cr（Ⅵ） in water is84.96%,76.77%,78.57%,51.99%and41.39%. As the initial concentration rising, the adsorptioncapacity of the five heavy metals also rose. Saturated adsorption amount is9.43mg/g,9.65mg/g,9.03mg/g,4.67mg/g and1.83mg/g respectively. The adsorptionconformed the pseudo-second-order equation and the Langmuir isotherm model. SEMpictures showed that secondary solid generated on the surface of oyster shell powderafter adsorbing Cu²⁺、Zn²⁺、Pb²⁺，and there was no obvious phenomenon on the oystershell powder after adsorbing Cd²⁺、Cr（Ⅵ）.2)Adding sodium dodecyl sulfonate （SDS） to the oyster shell powder aqueoussolution and preparing SDS-oyster shell powder. Orthogonal experiment was carriedout to explore the best modification process, results showed that the effect order ofdifferent modification conditions were modification time＞SDS dosage＞pH value＞modification temperature. The best modified condition of oyster shell powder was:SDS15%of oyster shell powder, modified time was120min, temperature was60℃,modification pH value was7. FTIR, SEM and EDS spectrum indicated that the modification was successful. The removal ratio of Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺ontomodified oyster shell powder was98.35%,93.29%,95.63%, respectively.3)Calcining oyster shell powder for5h at200℃,300℃,400℃,500℃and600℃, respectively. cooling, sifting, preparing thermal modified oyster shell powder andstudying its adsorptive property and characterization. The results showed that with theincrease of calcination temperature, the removal ratio of heavy metal ions hadincreased. The removal ratios of1mg/L Cu²⁺、Zn²⁺、Pb²⁺、Cd²⁺、Cr（Ⅵ）were up to98.23%,95.41%,95.25%,79.32%and79.35%onto oyster shell powder aftercalcining at600℃. FTIR, SEM and EDS spectrum indicated that the mainingredients of oyster shell powder after calcining were CaCO3and CaO.4)Selecting bentonite as accessory of water quality improver. Mixing oystershell powder and bentonite in proportion of2:1, and using pill-making machine toprepare water quality improver. The experiment indicated that it had a goodadsorption ability of Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Cr （VI） in water, and the adsorption ratiowere up to96.12%,87.32%,85.31%,88.32%and88.44%. This water conditionerwas spherical, the surface was rough, and it had much more porous structure andlarger specific surface area. It was good for adsorbing various pollutants.