Study On Preparation And Adsorption Behavior Of Copper Ions With Bentonite And Its Modified Bentonites

In this paper, the calcium bentonite, the sodium bentonite and the acid-modified bentonite adsorption materials were prepared from the Inner Mongolia Chifeng bentonite based on the excellent adsorption ability of bentonite to metal ions in the polluted water. The physical and chemical properties, the phase and the structure of the adsorption materials were analyzed. The connections among the compositions, the structures and the properties of the materials were studied by the method of FT-IR, XRD, XPS, ICP linkage analysis combined with the adsorption behavior and mechanism of adsorption material. The results showed that:The content of montmorillonite of the calcium bentonite increased by40.2%compared with the soil. The cation exchange capacity of the calcium bentonite increased from53.7mmol/100g to75.2mmol/100g after purification. The d(ooi) of the calcium bentonite became1.588nm compared to the orinigal vaule of soil and its specific surface area increased to2.67times with the orinigal value of soil. The d(ooi) of the modified sodium bentonite became1.223nm. The content of metal elements K, Ca, Mg, Al and its compounds of acid modified bentonite decreased obviously compared to that of calcium bentonite.The optimal adsorption process of the calcium bentonite, the sodium bentonite and the acid modified bentonite were fixed respectively based on the copper ion adsorption behavior of the three bentonite materials. The dynamic and thermodynamic analysis of copper ion adsorption material under the optimum conditions indicated that the copper ion adsorptions of the three adsorption materials all follows the pseudo-second order kinetic equation and Langmuir adsorption isotherm model which are absorbed as monolayer dominated by chemical absorption. The saturated adsorption capacities of the calcium bentonite, the sodium bentonite and the acid modified bentonite were7.79mg/g,24.91mg/g and7.42mg/g respectively. The adsorption process of the bentonite adsorption material to the copper ion is a pr o ce ss of sp on t a n eo u s, en dot he rm ic, ent r op y inc r e m ent. Ac c o r d i n g t o t h e r el at i o n sh i pbe t we e n t he ch a n g e of en tr op y an d con t en t of ad so rp ti on of co pp er i on t h e ab s o r p t i o n ofca l c i u m be n t o n i t e t o co pp e r i s mai nl y bas e d on the ion ex ch a n g e, i n cas e o f t h e so d i u mbe n t o n i t e i s ma i nl y b as e d on the ion exc h an g e a nd co or d in at ion, wh i l e t h e a b so r p t i o n of t h ea ci d mo d i f i ed b en t on i t e to co ppe r is ma in ly ba sed on the coo r di na t i on.T h e ch em i cal co m po si t io n, the i nte r l ay e r st r u ctu r e an d t he b o nd i n g st ru ct u r e o f t he t h r e ebe n t o n i t e ma t e r i al b ef o re an d af t er ad so r p ti on we r e an a lyz ed by t h e l i n k a g e a mon g FT-I R、XR D、 XP S a n d IC P. T he F I-I R s pec t r ogr am show ed tha t C u2+a nd gr an u l a r be n t o n i t e su r fa ceSi-OH a re mat ch ed wi th the sur f a ce com pl ex at ion re a ct io n. W he n t he ac i d-m o d i fi ed b en t on i t ea d so r b co p pe r i on, C u2+a n d cat ion of ei gh t hed r on la tt ic e ar e ma t c h ed wi t h t he co m p l e x a t i o nr eac t i o n b et w ee n l ay e r. T he XRD ind ic at ed tha t C u2+ha d en t er ed t he i n t e rl ay er of t h ebe n t o n i t e. Cu2p XP S sca ns of a cid-mod i fi e d be nto ni te ind ic at ed t ha t C u2+i s mat ch ed wi t h t heco mp l e x r eac t i o n i n st ea d of the i on ex cha nge re a ct ion. Usi n g ca l ci u m be n t o n i t e an d n at r i u mbe n t o n i t e ad so rb i ng co pp er ion s, t he a dso rp t io n man ner is the i o n s ex ch an g e, wh i l e t hea d so rp t i o n of t h e so d i um be nt oni te t o cop pe r i ons exi st s ma ti ng r ea ct i on si mu l t an eo u sl y.T h e a n al y si s o f I C P sh ow e d t hat t he cop p er i on is ma i n l y ad s o rb ed b y me an s ofco o r d i n at i on u si n g a cid-m o di f ied ben t on it e. I n cas e of u sin g the ca l c i u m b en t o ni t e ab s o r b i n gco p p er i on, t he co pp er ions ar e ab so rb ed by mea ns of i ons ex ch an g e. W hi l e i n cas e o f t h eso d i u m b en t on i t e, t he co pp er i ons ar e ab so r b ed by mea ns of the co o p e ra t i o n of i o n s ex ch an g ea n d co mp l e x a d so r p t i o n.