Study On Adsorption Of Cr(Ⅵ) In Water By Anaerobic Granular Sludge

With the rapid development of leather manufacturing,electroplating process,chromium and chromium salt production,chromium ore smelting and other industries,a large amount of wastewater containing chromium has caused great pollution to water body and environment.Anaerobic granular sludge is a kind of granular sludge formed by microbial accumulation under certain anaerobic culture conditions.As a biological adsorbent,it has high adsorption capacity,good solid-liquid separation effect and low price.The process is simple and can efficiently treat the water polluted by heavy metal and organic matter.Therefore,anaerobic granular sludge was used as adsorbent to treat Cr（Ⅵ）wastewater.A self-made anaerobic reactor with UASB reactor as model was studied.The operation conditions and operation process of the reactor were controlled.On the 60th day,the color of the reactor was gray and black,the particle size distribution was good,and the settling performance was very good.Mature anaerobic granular sludge with high microbial activity.Time,sludge dosage,initial concentration of pH,Cr（Ⅵ）and temperature all have some effects on the adsorption of Cr（Ⅵ）in anaerobic granular sludge.The best experimental conditions are as follows:The adsorption time is 72 h、the sludge dosage was 1 g（dry weight）/100 ml solution、the pH value is 7、sludge dosage is 1 g（dry weight）/100 ml solution、the temperature is 35℃.Cu（Ⅵ）plays an important role in the adsorption process.The adsorption process of Cr（Ⅵ）in water by anaerobic granular sludge experienced two stages:early rapid and late slow.The pseudo-second-order kinetic model can well describe the adsorption process of Cr（Ⅵ）by anaerobic granular sludge,and the experimental data can be fitted well by Freundlich and Langmuir isotherms.Compared with the experimental data,the Langmuir isothermal equation has a higher fitting correlation.The desorption experiment of Cr in anaerobic granular sludge showed that nitric acid was the most favorable desorption agent for recycling and regeneration of anaerobic granular sludge.The optimum desorption agent concentration and desorption time were 0.2 mol/L,60 min,.Under the optimum conditions,the desorption rate of Cr in anaerobic granular sludge by nitric acid was 98.84%.The adsorption mechanism of Cr（Ⅵ）in anaerobic granular sludge was studied by means of microbial activity test,Fourier transform infrared spectroscopy（FTIR）and XPS analysis.The results showed that the higher the microbial activity,the higher the adsorption mechanism of Cr（Ⅵ）from anaerobic granular sludge.The adsorption ability of anaerobic granular sludge to Cr（Ⅵ）in water is stronger.Fourier transform infrared spectroscopy（FTIR）analysis showed that OH,-NH₂,C-H,C=O,C-O-C and C-OH groups were involved in the adsorption of Cr（Ⅵ）in water by anaerobic granular sludge,and the main mechanism of adsorption was complexation.XPS scanning analysis showed that the Cr（Ⅵ）adsorbed by anaerobic granular sludge was basically reduced to Cr（Ⅲ）,which proved that the reduction was the most important role in the process of adsorption of Cr（Ⅵ）from anaerobic granular sludge.