摘要
采用共沉淀法,固定Mg^(2+)/(Al^(3+)+Ti^(4+))摩尔比为3.00,改变Ti^(4+)(/Al^(3+)+Ti^(4+))摩尔比(R_(Ti),0~0.40),合成了5个Mg-Al-Ti-CO_(3)层状双氢氧化物(LDHs)样品,并进行了表征.采用电势滴定、盐滴定和电势质量滴定法,测定了其结构电荷密度(σ_(st))、零净电荷点(pH_(PZNC))和零净质子电荷点(pH_(PZNPC))等,并基于普适1-pK和2-pK模型得出其表面羟基酸碱反应特征平衡常数(pK,pK^(int)_(a1)和pK^(int)_(a2)),考察了R_(Ti)对LDHs晶体结构和界面电化学性质的影响.研究结果表明,随着RTi增大,晶胞常数和层间距均增大,可归因于Ti^(4+)离子间强静电排斥作用.pH_(PZNC)和pH^(PZNPC)以及pK,pK^(int)_(a1)和pK^(int)_(a2)均随RTi的增大而有增大的趋势,表明表面羟基去质子化趋势降低.各LDHs样品的pH_(PZNPC)值低于其pH_(PZNC)值,且随电解质(NaNO_(3))浓度的增大而升高,可归因于结构正电荷效应.
Five Mg-Al-Ti-CO_(3) layered double hydroxides(LDHs)were synthesized using a coprecipitation method with a constant Mg^(2+)/(Al^(3+)+Ti^(4+)) molar ratio of 3.00 but varying Ti^(4+)(/Al^(3+)+Ti^(4+))molar ratio(RTi,0—0.40).Their structural charge density(σst),point of zero net charge(pH_(PZNC)),and point of zero net proton charge(pH_(PZNPC))were determined using potentiometric,salt and potentiometric mass titrations,and their intrinsic equilibrium constants of surface acid-base reactions(pK,pKint a1 and pKint a2)were estimated in turn based on the general 1-pK and 2-pK models.Special emphasis was placed on the effect of RTi on their crystal structure and interface electrochemical(IEC)proper⁃ties.With an increase in RTi,the cell constants(a,b and c)and d-spacing increase,arising from the strong electro⁃static repulsion between Ti^(4+)ions.An increase tendency was also observed for pH_(PZNC),pH_(PZNPC),pK,p^(Kint)_(a1),and p^(Kint)_(a2) with the increase of RTi,indicating a decrease in the deprotonation tendency of surface hydroxyl groups.In addition,it was observed that pH^(PZNPC) is lower than pH_(PZNC) and increases with increasing the electrolyte(NaNO_(3))concentration,arising from the effect of structural charges.This work provides a better understanding for the IEC properties of Ti^(4+)-containing LDHs.
作者
田震
杜娜
李海平
宋淑娥
侯万国
TIAN Zhen;DU Na;LI Haiping;SONG Shue;HOU Wanguo(Key Laboratory of Colloid&Interface Chemistry,Ministry of Education,Shandong University,Jinan 250100,China;National Engineering Technology Research Center of Colloidal Materials,Shandong University,Jinan 250100,China;School of Chemistry and Chemical Engineering,Shandong University,Jinan 250100,China)
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第4期94-103,共10页
Chemical Journal of Chinese Universities
基金
国家自然科学基金(批准号:21872082,21573133)
山东省自然科学基金(批准号:ZR2019MB025)资助.
关键词
层状双氢氧化物
零电荷点
界面酸碱反应
界面荷电模型
酸碱滴定
Layered doublehydroxide
Points ofzerocharge
Interface acid-base reaction
Interface-charging model
Acid-base titration
