Experimental Study On Adsorption Enhancement And Selective Removal Of Titanium Dioxide

As the typical photocatalysts,TiO₂ has attracted a great of attention in the environmental applications due to its high activity of catalysis,low price and non-toxicity.However,the applications of TiO₂ in wastewater treatment are limited by some blocks,such as its low adsorbability and non-selective catalysis.Adsorption is an inevitable stage of catalytic reaction.So it's of great significance to enhance the adsorptivity of TiO₂ for improving its removal efficiency to pollutants.Moreover,studies have shown that modification of TiO₂ with acid or base compounds can achieve selective photo-degradation to a certain extent.So,this paper chooses titanium dioxide as study object,and intends to use sodium carbonate?Na₂CO₃?as an inhibitor,absolute ethanol as a dispersant to synthetize alkali-modified TiO₂ nanomaterials via hydrothermal method for improving the removal efficiency and selective removal ability of TiO₂ for printing and dyeing wastewater.The main content is as follow:?1?Pure TiO₂ and different content of Na₂CO₃ modified TiO₂ nanomaterials were synthesized via the hydrothermal method.The properties of the different nanomaterials were tested with reactive yellow dyes,methylene blue dyes and basic fuchsin dyes,respectively.The results showed that the CO₃²-?0.01?/TiO₂ exhibited better photocatalytic activity compared with pure TiO₂ but didn't exhibit adsorptivity for all dyes?the removal rates of adsorption were less than 10.00%in 90min.?.However,the CO₃²-?0.15?/TiO₂ exhibited strong adsorption to methylene blue and basic fuchsin?the removal rates of basic fuchsin and methylene blue were 92.63%and 90.15%respectively after 15 minutes of adsorption.?,but didn't exhibit adsorption to active yellow.The nanomaterials were characterized by FT-IR,XRD and BET.The results showed that the CO₃²-group had been successfully modified into the CO₃²-?0.15?/TiO₂,which caused its grain size to decrease to 4.70nm,the specific surface area to increase to 77.55 m²·g^-1.This is the main reason why CO₃²-?0.15?/TiO₂ exhibited selective adsorptivity to cationic dyes.?2?Using methylene blue and basic fuchsin as contaminant models,the mechanism of adsorption of cationic dyes by CO₃²-?0.15?/TiO₂ was discussed.The results showed that the adsorption process of CO₃²-?0.15?/TiO₂ was dominated by chemisorption but supplemented by physisorption simultaneously and was an exothermic reaction.The separation factor RL calculated by the Langmuir model is between 0 and 1.0,1/n calculated by the Freundlich model is between 0.1 and 0.5,indicating that the adsorption approach of CO₃²-?0.15?/TiO₂ on both dyes belongs to "favorable adsorption",and its adsorption process was eassy to occur.Under the condition of 25?,the maximum adsorption capacity of CO₃²-?0.15?/TiO₂ for methylene blue and basic fuchsine were 84.89 mg·g^-1 and 20.80 mg·g^-1 respectively.?3?Using the aqueous mixture of fuchsin basic and reactive yellow dyes as contaminant model to verify the selective removal ability of pure TiO₂ and CO₃²-?0.15?/TiO₂.The results showed that the selectivity coefficients of pure TiO₂ and CO₃²-?0.15?/TiO₂ for basic fuchsin were 0.82 and 4.90,respectively.Compared with pure TiO₂,the adsorption amount of CO₃²-?0.15?/TiO₂ on basic fuchsine increased by 147.00%,while the adsorption amount of active yellow was only 41.20%of pure TiO₂.The CO₃²-?0.15?/TiO₂ exhibited selective removal efficiency via preferential adsorption of fuchsim basic from the aqueous mixture,which related to an increase of negative surface charge as compared to pure TiO₂.Our results of this study show that the CO₃²-?0.15?/TiO₂ nanomaterials with strong adsorbability can be obtained by adjusting the concentration of Na₂CO₃.The nanomaterials can preferentially adsorb a certain kind of organic pollutants in mixed solution and thus has selective removal ability,which has great practical significance and application value in the field of catalytic water treatment.