Biomineralization has become a research focus in wastewater treatment due to its much lower costs compared to traditional methods.However,the low sodium chloride(NaCl)-tolerance of bacteria limits applications to only water with low NaCl concentrations.Here,calcium ions in hypersaline wastewater(10％NaCl)were precipitated by free and immo-bilized Halouibrio mesolongii HMY2 bacteria and the differences between them were deter-mined.The results show that calcium ions can be transformed into several types of calcium carbonate with a range of morphologies,abundant organic functional groups(C-H,C-O-C,C=O,etc),protein secondary structures(β-sheet,α-helix,310 helix,and β-turn),P=O and S-H indicated by P2p and S2p,and more negative δ13CPDB(‰)values(-16.8‰ to-18.4‰).The opti-mal conditions for the immobilized bacteria were determined by doing experiments with six factors and five levels and using response surface method.Under the action of two groups of immobilized bacteria prepared under the optimal conditions,by the 10th day,Ca2+ion pre-cipitation ratios had increased to 79％-89％and 80％-88％with changes in magnesium ion cencentrations.Magnesium ions can significantly inhibit the calcium ion precipitation,and this inhibitory effect can be decreased under the action of immobilized bacteria.Minerals induced by immobilized bacteria always aggregated together,had higher contents of Mg,P,and S,lower stable carbon isotope values and less well-developed protein secondary struc-tures.This study demonstrates an economic and eco-friendly method for recycling calcium ions in hypersaline wastewater,providing an easy step in the process of desalination.

College of Chemical and Biological Engineering,College of Safety and Environmental Engineering,College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China;Laboratory for Marine Mineral Resources,Center for Isotope Geochemistry and Geochronology,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266237,China;School of Earth Sciences,University of Bristol,Bristol BS8 1RJ,UK;Cabot Institute,University of Bristol,Cantock's Close,Bristol BS8 1UJ,UK

[1]Huaxiao Yan;Meiyu Huang;Jihan Wang;Heding Geng;Xiyu Zhang;Ziyang Qiu;Yongliang Dai;Zuozhen Han;Yudong Xu;Long Meng;Lanmei Zhao;Maurice E.Tucker;Hui Zhao-.Difference in calcium ion precipitation between free and immobilized Halouibrio mesolongii HMY2)[J].环境科学学报（英文版）,2022(12):184-200

Halouibrio,mesolongii,HMY2,Biomineralization,immo,P2p,S2p,Ca2+ion,cencentrations

Difference,calcium,precipitation,between,free,immobilized,has,become,research,focus,wastewater,treatment,due,much,lower,costs,compared,traditional,methods,However,sodium,chloride,NaCl,tolerance,bacteria,limits,applications,only,concentrations,Here,hypersaline,were,precipitated,by,differences,them,results,show,that,transformed,into,several,types,carbonate,range,morphologies,abundant,organic,functional,groups,etc,protein,secondary,structures,sheet,helix,turn,indicated,more,negative,13CPDB,values,conditions,determined,doing,experiments,six,factors,five,levels,using,response,surface,Under,action,two,prepared,under,optimal,10th,day,ratios,had,increased,changes,magnesium,Magnesium,significantly,this,inhibitory,effect,decreased,Minerals,induced,always,aggregated,together,higher,contents,Mg,stable,isotope,less,well,developed,This,study,demonstrates,economic,friendly,recycling,providing,easy,step,process,desalination

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