Study On Calcium Sulphate Whisker Application In Wastewater Treatment

Printing-dyeing and high ammonia nitrogen wastewater sources are widely used in textile-dyeing,landfill and aquaculture industries.Their chemical oxygen demand?COD?,suspended substance?SS?,chromaticity and/or ammonia nitrogen are high.These kinds of wastewaters are treated by using the biological process combined with physicochemical technologies.Adsorption is the common technology of physical and chemical adsorption for removing chromaticity and ammonia nitrogen.The effects of the optimal conditions,such as absorbent concentration,temperature,reaction time and pH value on the decolorization performance of treating the printing-dyeing wastewater with calcium sulfate whisker?CSW?were investigated.The mechanisms and models of decolorization and ammonia nitrogen-removal were also envisaged.The results showed that during the application of CSW in the dye wastewater decolorization the suitable conditions were as follows:?1?100 g/L CSW,adsorption time 60 min,pH 8.0,temperature 30?,in which water chromaticity and total organic carbon?TOC?removal rate was 88% and 45% respectively.?2?With increasing pH value of dye wastewater,the decolorization rate showed an increase trend.When the pH value of the wastewater increased to 8.0,the maximum decolorization and TOC removal rates were obtained to be 86.57% and 44.56% respectively.?3?With the increase of the temperature,the decolorization rate of dye wastewater by CSW decreased from 86.57% to 77.53%.In addition,the TOC removal rate of the dye wastewater reduced from 44.56% to 28.97%.Therefore,ambient temperatures ranges from 20 to 30? were suitable for the adsorption of dye wastewater by the CSW.?4?Under the conditions of concentrations?50-300 mg/L?direct indigo 30 ?,pH8.0 and 100 g/L CSW,the dye adsorption performance through CSW decreased from 95.58%?50 mg/L direct indigo?to the lowest removal of 69.35%?300 mg/L direct indigo?.Using the CSW to adsorb ammonia nitrogen?NH₄⁺-N?showed that:?1?The optimum conditions of pH and adsorbent concentration were 8.0 and 15 g/L,respectively.?2?Under the conditions of 100 mg/L of NH₄⁺-N,15g/L of CSW,pH of 8 and wastewater temperatures of 20-50?,the adsorption efficiencies of NH₄⁺-N by CSW were 83.3% and 54.2%,respectively.?3?With the increase of the initial concentration of NH₄⁺-N,the CSW on the ammonia adsorption efficiencies decreased from 96.7%?50 mg/L of initial NH₄⁺-N?to the lowest removal rate of 53.2%?400 mg/L of initial NH₄⁺-N?.?4?It was shown that the NH₄⁺-N adsorption with the CSW could well be characterized with Langmuir and Freundlich modes,and that the maximum NH₄⁺-N adsorptive capacity with CSW was obtained to be 15.82 mg/g.