| Sludge is scum and sediment produced after sewage treatment,with the characteristics of large production,easy to smell,hard to dehydration,etc,it needs to be harmless treatment and resource utilization to avoid secondary pollution.Sludge solidification/stabilization is a common method for sludge disposal,it mainly use sludge curing agent to solidify and store pollutants,but there are problems after curing such as low compression strength,low resource utilization rate,capacity reduction and secondary pollution.The cemented-based sludge curing agent has not yet got rid of cemented material,but the geopolymer known as“Green cement”are considered to be the best cement substitute with advantages of high compression strength and corrosion resistant.This work carrying out an innovative study on sludge solidification and resource recycling utilization of geopolymer guided by energy saving,waste resource utilization and high efficiency.The main results are as followed:Preparation test of geopolymer shows that taking volcanic rocks,metakaolin and alkali activators as raw materials,the optimal ratio obtained by orthogonal test is:1.5grey alkali ratio,1.5 alkali activator modulus,20%volcanic rocks,0.6 water-cement ratio.The compression strength for 3 days is 9MPa by standard curing,the increase in medium and long time is not obvious which reflects the early strength,rapid setting and long-term stability is good for sludge solidification,and the addition of volcanic rock reaction activity is beneficial to early strength.The XRD analysis indicated that the internal structure of geopolymer is amorphous without new crystal appear.The FTIR analysis showed that there were asymmetric and non-uniform stretching vibration of Si-O-Si and Al-O-Si and shift to low absorption peak wave,indicating the geopolymer reaction has occurred.The SEM morphological characterization showed that the interior of geopolymer was a dense layered space structure consisted by resembled coral reefs,uneven layers and sheets.Preparation of the geopolymer-based composite sludge curing agent and the sludge curing process parameters experiments show that orthogonal tests were performed with mechanical properties as indicators and the optimal ratio was as follows:40%geopolymer gelling agent,15%quicklime coagulant,10%dental plaster products enhancer,25%cinder skeleton material,0.3%nano silica additive.The optimal ratio of sludge was 62.5%,the maximum compression strength of 3d and 28d was 3.72MPa and14.60MPa which met both the requirements of resource utilization strength and the national standard（GB/HJ-2010）and（GB/T23485-2009）.The mechanical stability test,moisture content test,heavy metal toxicity test,anti-leaching performance test,sludge capacity ratio test,static corruption test and traditional sludge curing agent were carried out respectively,which showed that the geopolymer-based composite sludge curing agent solidified sludge was feasible and possessed great excellent performance.There are 4reaction stage in sludge solidification mechanism.The No.2 curing process（liquid alkali activator solidified and ground into power+curing agent solid phase material（mix1）+sludge（mix2））was determined as the best on-site construction process,and the curing cost was 689.55 yuan/ton.Resource recycling utilization of sludge to prepare sponge urban sludge permeable bricks.The results determined the best formula of sludge permeable bricks as follows:54.6%sludge,32.8%geopolymer-based composite sludge curing agent,10.9%construction waste fine aggregate,1.7%foaming agent,and the optimal preparation process parameters were as follows:billet by drying pressed（30MPa）,steam curing（110℃,20h）,blast drying（75℃,5h）.After standard curing for 7 days,the sludge permeable bricks with compression strength of 30MPa and permeability coefficient greater than 1.0×10-2cm/s could be obtained,reached above grade B permeability coefficient of standard（GB/T25993―2010）.The single cost of sponge urban sludge permeable bricks is 0.82 yuan. |
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