两种胶原纤维固化单宁对La3+的吸附特性研究

以皮胶原纤维为基质,通过交联剂分别将黑荆树单宁和杨梅单宁固化在胶原纤维上制备吸附材料。实验表明,这两种吸附材料对稀土金属离子La^3＋有很好的吸附作用。在pH为4.5的条件下,当吸附剂用量为0.1 g,La^3＋初始浓度为9.952 mmol·L^-1,固化杨梅单宁的平衡吸附量为0.388 mmol·g^-1,比固化黑荆树单宁略大,其吸附平衡均符合Freundlich方程。进一步研究了固化杨梅单宁的吸附动力学、温度、pH值等对吸附平衡的影响。结果表明,温度对吸附平衡的影响不明显;pH值对吸附平衡有较大影响,在适当范围内提高pH值会增加平衡吸附量;吸附动力学可用拟二级速度方程来描述。当吸附温度为293 K时,由拟二级速率方程计算所得的平衡吸附量与实测的平衡吸附量误差在3%以内。同时固化杨梅单宁也具有良好的柱动力学特性。     

胶原-单宁树脂的制备及其对水溶液中UO2+2的吸附特性研究

以天然牛皮为原料,经胃蛋白酶处理制得水解胶原;通过胶原-黑荆树单宁-醛反应制备了胶原-单宁树脂(C-TR)吸附材料,并表征了材料的形貌,测定了材料的比表面积、热变形温度等性质。系统研究了C-TR对水溶液中UO22 的吸附特性。结果表明,C-TR对UO22 有较强的吸附能力。当温度为303K、pH=5.0、UO22 的初始浓度2.5mmol.L-1时,吸附容量达到1.49mmolU/g。升高温度,平衡吸附量增大。pH对吸附容量的影响较大,适宜的pH范围为5.0-6.0。C-TR对UO22 的吸附平衡符合Freundlich方程。吸附动力学可用拟二级速度方程来描述。C-TR对UO22 的吸附基本不受NaCl影响,该吸附材料可望用于海水中铀的富集和分离。     

胶原纤维固化杨梅单宁对UO22+的吸附

以胶原纤维为基质，通过交联剂将杨梅单宁固化在胶原纤维上制备吸附材料．实验结果表明，所制备的吸附材料对UO2^2 具有很强的吸附能力，当溶液中UO2^2 的浓度为7．5mmol/L、pH为5．0时，吸附容量达到1．19mmol UO2^2 /g(283．3mgU／g)．UO2^2 在固化杨梅单宁上的吸附平衡符合Freurldlich方程，升高温度，平衡吸附量增大。吸附动力学可用拟二级速度方程来描述，由动力学方程计算得到的平衡吸附量与实测的平衡吸附量基本相同，误差在4％以内．pH值对吸附过程有较大影响，适宜的pH在5-8之间。所制备的吸附材料具有优良的柱动力学特性，床层的有效利用率高；经解吸后的吸附柱其吸附性能基本不变。     

全钒液流电池高浓度下V(IV)/V(V)的电极过程研究

采用循环伏安、低速线性扫描和阻抗技术, 以石墨为电极, 研究了V(IV)/V(V)在较高浓度下的电极过程. 结果表明, 采用2.0 mol•L-1 的V(IV)溶液时, H2SO4浓度低于2 mol•L-1, V(IV)/V(V)反应极化大, 可逆性差, 表现为电化学和扩散混合控制; H2SO4浓度增至2 mol•L-1以上, V(IV)/V(V)反应的可逆性提高, 转为扩散控制, 且增加H2SO4浓度有利于阻抗的降低; 但H2SO4浓度超过3 mol•L-1, 溶液的粘度和传质阻力大, 阻抗反而增大. 在3 mol•L-1的H2SO4中, 随着V(IV)浓度的增加, 体系的可逆性和动力学改善, 阻抗减小; 但V(IV)浓度超过2.0 mol•L-1, 较高的溶液粘度导致溶液的传质阻力迅速增加, V(IV)/ V(V)的电化学性能衰减, 阻抗增大. 因此, 综合考虑电极反应动力学和电池的能量密度两因素, V(IV)溶液的最佳浓度为1.5～2.0 mol•L-1, H2SO4浓度为3 mol•L-1.     

不同吸附模式对As(V)在TiO2颗粒上亚稳态吸附的影响

通过对比As(V)在TiO₂颗粒上的柱(column)吸附和静态(batch)吸附行为, 研究了柱吸附和静态吸附两种反应模式对该体系亚稳态吸附的影响. 在相同热力学条件下, 将总量一定的As(V)溶液分别加入柱吸附和静态吸附体系中. 结果表明, 随着吸附模式的改变, 静态吸附体系比柱吸附体系更快达到吸附平衡, 静态吸附体系平衡吸附量(0.42 mg·g^-1)明显高于柱吸附体系平衡吸附量(0.25 mg·g^-1), 且静态吸附体系的吸附不可逆性弱于柱吸附体系的吸附不可逆性. 说明溶质吸附模式(动力学条件)的改变使得相同热力学条件下的吸附反应达到了不同的平衡状态. 柱吸附和静态吸附实验中, As(V)在TiO₂颗粒上的液膜扩散系数、总传质系数及吸附平衡后形成的微观吸附状态均不同, 共同导致了两种反应宏观吸附行为上的差异.     

不同吸附模式对As(V)在TiO2颗粒上亚稳态吸附的影响

通过对比As(V)在TiO2颗粒上的柱(column)吸附和静态(batch)吸附行为,研究了柱吸附和静态吸附两种反应模式对该体系亚稳态吸附的影响.在相同热力学条件下,将总量一定的As(V)溶液分别加入柱吸附和静态吸附体系中.结果表明,随着吸附模式的改变,静态吸附体系比柱吸附体系更快达到吸附平衡,静态吸附体系平衡吸附量(0.42 mg·g-1)明显高于柱吸附体系平衡吸附量(0.25 mg·g-1),且静态吸附体系的吸附不可逆性弱于柱吸附体系的吸附不可逆性.说明溶质吸附模式(动力学条件)的改变使得相同热力学条件下的吸附反应达到了不同的平衡状态.柱吸附和静态吸附实验中,As(V)在TiO2颗粒上的液膜扩散系数、总传质系数及吸附平衡后形成的微观吸附状态均不同,共同导致了两种反应宏观吸附行为上的差异.     

皮胶原纤维对单宁的选择性吸附

用动物皮为原料制备皮胶原纤维吸附材料, 研究了这种吸附材料对单宁的吸附特性. 结果表明, 皮胶原纤维对单宁具有非常好的吸附选择性和高吸附容量, 通过一次吸附, 单宁的去除率可达90%以上, 而其他有效成分损失率小于10%. 单宁在胶原纤维上的吸附属于氢键吸附; 其吸附平衡符合Freundlich方程; 其吸附动力学符合拟二级速度方程.     

新型载锆树脂除As(V)的研究

通过研究4种不同树脂负载锆后去除As(V)的性能,筛选出最佳锆载体为强碱性阴离子交换树脂D201。通过正交实验对载锆树脂制备工艺进行优化,获得最佳载锆条件为:Zr OCl2加入量10g,HCl-Na Cl摩尔比为0.3:0.3(共0.6mol),温度为30℃。研究了不同条件下D201-Zr对As(V)的吸附性能,结果表明,D201-Zr吸附As(V)的最佳p H值为7.0;最大吸附量为83.24mg/g;其对砷酸盐的吸附平衡时间很短,在60min之内基本可以达到吸附平衡;吸附动力学可以用拟二级动力学方程表达;吸附等温线符合Langmuir单分子层吸附模型;C1-、SO42-等对D201-Zr吸附砷酸盐的影响较小,而PO43-的影响较大。柱实验表明,D201-Zr对砷酸钠不仅有很好的去除效果,而且处理量很大。模拟水样经处理后As(V)浓度低于10μg/L,可以满足中国饮用水标准的规定。吸附后的D201-Zr可用Na OH-Na Cl(质量分数均为5%)混合液进行洗脱再生,反复使用多次后吸附能力未下降。     

多胺型阴离子交换纤维吸附铬(VI)的动力学

以聚丙烯腈纤维为原料, 采用化学改性法, 制备了多胺型阴离子交换纤维. 研究该纤维对Cr(VI)的吸附特性. 在研究的温度及浓度范围内, 该纤维对Cr(VI)吸附的平衡数据符合Langmuir和Freundlich吸附等温方程, 对Cr(VI)有较强的亲和力, 吸附反应易于进行. 重点研究了该纤维对Cr(VI)的吸附动力学特性, 分别采用Lagergren一级动力学方程、修正伪一级动力学方程、伪二级动力学方程和颗粒内扩散方程进行拟合, 计算相应的速率常数. 研究表明, 该吸附是一个快速吸附过程, 20 min即可接近吸附平衡, 吸附过程符合伪二级动力学方程, 以化学吸附为主, 该纤维能够多次反复对Cr(VI)进行吸附.     

磁性石墨烯对结晶紫的吸附性能研究

本文研究了磁性石墨烯对结晶紫的吸附特性,考察了pH、吸附剂用量、结晶紫浓度以及温度等对吸附平衡的影响。磁性石墨烯吸附结晶紫符合准二级动力学模型。不同温度下磁性石墨烯对结晶紫的吸附等温线满足Langmuir方程(R20.99)、Freundlich方程(R20.97)以及D-R模型(R20.96)。吸附热力学计算结果表明该吸附过程的△G0,并且随着温度升高△G越来越小,表明该吸附反应是自发进行的吸热反应。     

Recovery of Th(IV) from aqueous solution by reassembled collagen-tannin fiber adsorbent

A novel adsorbent, collagen immobilized tannin adsorbent (CITA), was prepared and its adsorption behaviors to Th(IV) were investigated. CITA was in fibrous state due to the reassembly of collagen molecules by the inducement of tannin. This adsorbent loaded a greater amount of tannin and exhibited higher adsorption capacity to Th(IV) than the tannin immobilized adsorbent prepared from collagen fiber. The adsorption of CITA to Th(IV) is mainly attributed to surface complexation, which is a pH- rather than an ionic strength-dependent process. The adsorption kinetics and isotherms were described by pseudo-second-order rate model and Freundlich equation, respectively. Column adsorption studies indicated that CITA is available for effectively recovering Th(IV) from aqueous solution.     

Adsorption recovery of thorium(IV) by Myrica rubra tannin and larch tannin immobilized onto collagen fibres

Novel adsorbents which can concentrate Th(IV) in aqueous solution were prepared by immobilizingMyrica rubra tannin and larch tannin onto collagen fibre matrices. The adsorption capacities of the immobilized tannins to Th(IV) are related to temperature and pH value of the adsorption process. For example, when the initial concentration of Th(IV) was 116.0 mg·l^-1 and the immobilized tannin was 100 mg, the adsorption capacities of immobilized Myrica rubra tannin and larch tannin were 55.98 mg Th(IV)·g^-1 and 13.19 mg Th(IV)·g^-1, respectively at 303 K, and 73.67 mg Th(IV)·g^-1 and 18.19 mg Th(IV)·g^-1 at 323 K. It was also found that the higher adsorption capacity was obtained at higher pH value. The adsorption equilibrium data of the immobilized tannins for Th(IV) can be well fitted by the Langmuir model and the mechanism of the adsorption was found to be a chemical adsorption. In general, the adsorption capacity of immobilized Myrica rubra tannin to Th(IV) is significantly higher than that of immobilized larch tannin, probably due to the fact that the B ring of Myrica rubra tannin has a pyrogallol structure which has higher reaction activity with metal ions. The breakthrough point of the adsorption column of immobilized Myrica rubra tannin was at 33 bed volumes for the experimental system. The mass transfer coefficient of adsorption column determined by Adams-Bohart equation was 1.61·10^-4 l·mg^-1.min^-1. The adsorption column can be easily regenerated by 0.1 mol·l^-1 HNO₃ solution, showing outstanding ability of concentrating Th(IV). This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigation on Concentrated Ⅴ（Ⅳ）/Ⅴ（Ⅴ） Redox Reaction by Rotating Disc Voltammetry

The kinetic characteristics of the concentrated Ⅴ（Ⅳ）/Ⅴ（Ⅴ） couple have been studied at a glassy carbon electrode in sulfuric acid using rotating-disc electrode and cyclic voltammetry. The kinetics of the Ⅴ（Ⅳ）/Ⅴ（Ⅴ） redox couple reaction was found to be electrochemically quasi-reversible with the slower kinetics for the Ⅴ（Ⅴ） reduction than that for the Ⅴ（Ⅳ） oxidation. And, dependence of diffusion coefficients and kinetic parameters of Ⅴ（Ⅳ） species on the Ⅴ（Ⅳ） and H2SO4 concentration was investigated. It is shown that the concentration of active species Ⅴ（Ⅳ） should be over 1 mol·L^-1 for the redox flow battery application. Further, with increasing the Ⅴ（Ⅳ） and H2SO4 concentration, the diffusion coefficients of Ⅴ（Ⅳ） were gradually reduced whereas its kinetics was improved considerably, especially in the case of Ⅴ（Ⅳ） and H2SO4 up to 2 and 4 mol·L^-1.     

Adsorption of metal anions of vanadium(V) and chromium(VI) on Zr(IV)-impregnated collagen fiber

The metal anions of vanadium (V) and chromium (VI) in aqueous solution can be effectively adsorbed by Zr(IV)-impregnated collagen fiber (ZrICF). The maximum adsorption capacity of V(V) takes place within the pH range of 5.0 to 8.0, while that of Cr(VI) is within the pH range of 6.0 to 9.0. When the initial concentration of metal ions was 2.00 mmol L⁻¹ and the temperature was 303 K, the adsorption capacity of V(V) on Zr-ICF was 1.92 mmol g⁻¹ at pH 5.0, and the adsorption capacity of Cr(VI) was 0.53 mmol g⁻¹ at pH 7.0. As temperature increased, the adsorption capacity of V(V) increased, while that of Cr(VI) was almost unchanged. The adsorption isotherms of the anionic species of V(V) and Cr(VI) can be fit by the Langmuir equation. The adsorption rate of V(V) follows the pseudo-first-order rate model, while the adsorption rate of Cr(VI) follows the pseudo-second-order rate model. Furthermore, ZrICF shows high adsorption selectivity to V(V) in the mixture solution of V(V) and Cr(VI). Practical applications of ZrICF could be expected in consideration of its performance in adsorption of V(V) and Cr(VI).     

Surface-modified carbon black for As(V) removal

This paper reports the results of the adsorption performance of As(V) removal by a commercial carbon black and its H2SO4-modified form in a single-ion situation. The influence of different process parameters and the physicochemical principles involved were studied in detail. Acid modification caused morphological changes in the virgin carbon black as evidenced by BET surface area measurements and SEM study. FTIR spectra showed the introduction of sulfonic acid group in the parent carbon due to H2SO4 treatment. TGA analysis revealed higher weight loss characteristics of the modified carbon, demonstrating the creation of functional groups. The point of zero charge (pH pzc) of the modified carbon black is highly acidic (3.5) compared to commercial carbon black (6.4). It directly infers the generation of acidic functional moieties in the carbon black. The adsorption experiments were carried out following batch equilibrium techniques. The kinetics and thermodynamics of adsorption were investigated to unveil the mechanism and nature of the adsorption process, respectively. The kinetic parameters of different models were calculated and discussed. The kinetics of adsorption can be expressed by a pseudo-second-order model and intraparticle diffusion was not the rate-determining step. Dependence of pH on adsorption showed maximum metal uptake in the range of 4-5 and inferred surface complexion as the principal mechanism of adsorption. The equilibrium adsorption data were modeled using Freundlich, Langmuir, and Dubinin-Kaganer-Radushkevich (DKR) isotherm equations and the corresponding isotherm parameters were calculated and discussed in detail.     

Corrosion inhibition performance of tannins for mild steel in hydrochloric acid solution

Research on Chemical Intermediates - The corrosion inhibition behavior of commercial hydrolysable tannin (tara tannin), condensed tannin (black wattle tannin) and complex tannin (bayberry tannin)...     

ADSORPTION OF TANNIN FROM AQUEOUS SOLUTION ONTO MACROPOROUS CROSSLINKED POLY（N—VINYL—ACETAMIDE）VIA HYDROGEN BONDING

A Strongly hydrophilic hydrogen-bonding adsorbent-macroporous crosslinked Poly(Nvinyl-acetamide),which contain both hydrogen bond acceptor and donator,was synthesized.Adsorption mechanism and dynamic adsorption of tannin from aqueous solution onto the adsorbent were investigated.Most of the differntial adsorption heats for various adsorption capacities calculated from the adsorption isotherms according to Clapeyron-Clausius equation lay in the range of hydrogen bond energy(8-50J/mol).Adsorption properties of the adsorbent were studied in detail.These results revealed a hydrogen bonding mechanism of the adsorption of tannin from aqueous solution onto the adsorbent.The result of the dynamic adsorption of tanning with the initial concentration under 600mg/L showed that the adsorption rate of tannin exceeded 90% when the flow rate was 3BV/h and the effluent volume reached 100BV.Therefore,the developed hydrogen-bonding adsorbent-macroporous crosslinked poly(N-vinyl-acetamide)-is an excellent adsorbent to remove tannin from extract of natural products,and has great value in application.     

The kinetics of condensation of phenolic polyflavonoid tannins with aldehydes

The rate constants and free energies of activation of the acid-and base-catalyzed reactions of floroglucinolic and resorcinolic flavonoid A rings of pine and wattle tannins, respectively, as well as the model compounds resorcinol, floroglucinol, and catechol, with formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, and furfural, were obtained. Second-order kinetics were found to fit these reactions. Indication and proof of the existence of unstable aldehyde ether bridges and their fast rearrangement at ambient temperature to alkyl bridges for fast-reacting phenols or phenolic compounds, such as tannins, were obtained for the first time. The dependence of the reaction kinetics on the concentration of OH- catalyst was investigated. Anomalies in the behavior of wattle tannin with aldehydes and n-butyraldehyde with phenols were observed and partially explained. The results led to a slightly different interpretation of the wattle tannin flavonoid structure.