| Textile industry has caused serious environmental pollution mainly because of its sewage. Dyeing sludge-by-product of wastewater treatment has been treated unsuccessfully,leading serious pollutions.The situation of the dealing of sludge is increasingly rigorous in China.So it is necessary to investigate applied research on how to deal with and recovery from dyeing sludge according to the Chinese situation.In this paper,firstly the characteristics of dyeing sludge and the methods of its recycling at home and abroad were summarized.Based on the summarization of the recycling methods used by the predecessors,"the acid dissolution and neutralization method" combined process was chosen to prepare PAS from dyeing sludge.The objective of this research is to offer a more useful and economical process for Al recovery from dyeing sludge.The frame of the paper is as follows:analysis of the component and content of metals in dyeing sludge,acid dissolution of Al from dyeing sludge,preparation of PAS by neutralization method,and the coagulant effect of PAS.In first,the paper analysed the characters of dyeing sludge and discussed the optimal experiment conditions of acid dissolution of Al.The effect of temperature on organic matter and percentage of weight loss of dyeing sludge were emphatically observed.The component and content of metals,the forms of Al in the dyeing sludge before and after combustion were investigated.And single factor experiments under different kinds of acid,addition amount of acid, recation temperature,recation time and liquid-solid ratio were also conducted to find out the optimal conditions of acid dissolution of Al.The results indicated that the metals in the sludge are Al,Ca,Fe,Mg,etc.The amounts of Al are 157 and 248mg/g before and after combustion respectively.High temperature could decompose humic acid and transform Al into the form that could be leached by acid.In leaching experiments with four kinds of acid,leaching rate of Al kept similar level when HCl,HNO3 and H2SO4 were used,and the rate of Al with H3PO4 was the lowest.But considering balance among addition amount and colatilization of HCl,and high cost and potential eutrophication caused by HNO3,H2SO4 was chosen to conduct the experiment finally.The most optimized qualifications of acid leaching Al from dyeing sludge were elicited: the addition amount of H2SO4 0.92mL/g,the leaching time 3hr,the ratio of liquid to solid 5ml/g, leaching Al at normal temperature(25℃),Al leaching recovery can reach at 96.7%.Secondly,the paper investigated the optimal condition of preparation of PAS in neutralization method.The effect of different kinds of basification agent,way of adding,Ca(OH)2:Al2(SO4)3 and temperature on the species distribution of Al in PAS and coagulation effect was studied.Alb%, basicity and coagulation effect were observed to be higher,when PAS was prepared by Ca(OH)2, Ca(OH)2:Al2(SO4)3 was set 1.8:1,and its driping was positive and slow at 85℃.In addition,Citric acid was the best stabilizer for PAS prepared from leaching solution of sludge.By the addition of citric acid,PALS becomes more stabilized.Thirdly,the paper compared the coagulation effect of PAS prepared in above mentioned way, PAS and AS purchased on simulative and practical dyeing wastewater.At last,the paper discussed the amount of residue of Al after coagulation.The results showed that the optimal pH was among 6.5～8.5.Compared with PAS prepared from dyeing sludge,PAS purchased shows higher coagulation effect.The amount of residue of Al was less than 1mg/L while addition amount of coagulation was increased from 10mL/L to 50ml/L,and theirs residue of Al was less than AS.
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