title: Modeling and optimization of lime-based stabilization in high alkaline arsenic-bearing sludges with a central composite design.
abstract: This study focuses on the modeling and optimization of lime-based stabilization in high alkaline arsenic-bearing sludges (HAABS) and describes the relationship between the arsenic leachate concentration (ALC) and stabilization parameters to develop a prediction model for obtaining the optimal process parameters and conditions. A central composite design (CCD) along with response surface methodology (RSM) was conducted to model and investigate the stabilization process with three independent variables: the Ca/As mole ratio, reaction time and liquid/solid ratio, along with their interactions. The obvious characteristic changes of the HAABS before and after stabilization were verified by X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size distribution (PSD) and the community bureau of reference (BCR) sequential extraction procedure. A prediction model Y(ALC)with a statistically significant P-value <0.01 and high correlation coefficient R2= 93.22% was obtained. The optimal parameters were successfully predicted by the model for the minimum ALC of 0.312 mg/L, which was validated with the experimental result (0.306 mg/L). The XRD, SEM and PSD results indicated that crystal calcium arsenate Ca5(AsO4)3OH and Ca4(OH)2(AsO4)2·4H2O formation played an important role in minimizing the ALC. The BCR sequential extraction results demonstrated that the treated HAABS were stable in a weak acidic environment for a short time but posed a potential environmental risk after a long time. The results clearly confirm that the proposed three-factor CCD is an effective approach for modeling the stabilization of HAABS. However, further solidification technology is suggested for use after lime-based stabilization treatment of arsenic-bearing sludges.
authors.affiliation: a Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University , Changsha , China.
authors.forename: Jie
authors.initials: J
authors.lastname: Lei
authors.affiliation: a Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University , Changsha , China.|b Chinese National Engineering Research Center for Control and Treatment of Heavy Metal Pollution , Changsha , China.
authors.forename: Bing
authors.initials: B
authors.lastname: Peng
authors.affiliation: a Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University , Changsha , China.|b Chinese National Engineering Research Center for Control and Treatment of Heavy Metal Pollution , Changsha , China.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Min
authors.affiliation: a Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University , Changsha , China.|b Chinese National Engineering Research Center for Control and Treatment of Heavy Metal Pollution , Changsha , China.
authors.forename: Yanjie
authors.initials: Y
authors.lastname: Liang
authors.affiliation: a Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University , Changsha , China.
authors.forename: Yang
authors.initials: Y
authors.lastname: You
authors.affiliation: a Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University , Changsha , China.|b Chinese National Engineering Research Center for Control and Treatment of Heavy Metal Pollution , Changsha , China.
authors.forename: Liyuan
authors.initials: L
authors.lastname: Chai
mesh_terms: D000468:Alkalies / Q000737:chemistry*; D001149:Arsenates / Q000737:chemistry; D001151:Arsenic / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D002138:Calibration; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008962:Models, Theoretical; D010087:Oxides / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: D000468:Alkalies; D001149:Arsenates; D017610:Calcium Compounds; D010087:Oxides; D012722:Sewage; C045817:calcium arsenate; C016538:lime; D001151:Arsenic
keywords: Arsenic-bearing sludges; BCR sequential extraction; calcium arsenate crystallization; central composite design; optimization; response surface methodology; stabilization