Kinetics of chromate reduction by pyrite and biotite under acidic conditions

2006 ◽  
Vol 21 (9) ◽  
pp. 1469-1481 ◽  
Author(s):  
Chul-Min Chon ◽  
Jae Gon Kim ◽  
Hi-Soo Moon
2018 ◽  
Vol 20 (2) ◽  
pp. 408-416

Mesophilic biomass and thermophilic biomass samples were isolated and used to remove Dorasyn Red dye from aqueous solutions. The biosorption kinetics of dye uptake by four different types of biomass at three temperatures (20, 30, and 40 °C) were investigated using pseudo-first order kinetics, pseudo-second order kinetics, intraparticle diffusion, Elovich, and Bangham models. The pseudo-second-order kinetics model and the first stage of the intraparticle diffusion model were effective in describing the experimental kinetics data. The biosorption results showed that the mesophilic biomass samples could be useful for removing dye under acidic conditions.


Author(s):  
Luigi Monsù Scolaro ◽  
Ilaria Occhiuto ◽  
Mariachiara Trapani ◽  
ROBERTO ZAGAMI ◽  
Andrea Romeo ◽  
...  

The zinc(II) metal derivative of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) is quite labile and readily demetallates under acidic conditions, affording the parent diacid porphyrin in a monomeric form. The rate of this process is first order on [ZnTPPS4] and second order on [H+], allowing a precise control of the monomer release in solution. Under high ionic strength, this latter species is able to self-assemble into J-aggregates, whose kinetics of growth are largely modulated by pH. The aggregation kinetics have been treated according to a well-established model, in which the formation of an initial nucleus is the rate determining step preceding the autocatalytic growth of the whole assembly. The extinction spectra of the aggregates suggest the occurrence of a dipolar coupling mechanism very similar to that operating in metal nanoparticles. Spontaneous symmetry breaking takes place in these aggregates as evidenced by unusual circular dichroism spectra. The intensity and sign of the effect is controlled by the aggregation rate and therefore can be tuned through a proper choice of initial conditions.


2011 ◽  
Vol 1301 ◽  
Author(s):  
N. Watanobe ◽  
T. Yoshioka ◽  
T. Ikoma ◽  
T. Kuwayama ◽  
T. Higaki ◽  
...  

ABSTRACTThe dissolution kinetics of type B carbonate apatite (CAp) disks sintered at different temperatures were investigated under acidic conditions similar to an osteoclastic desorption process in bone remodeling. The type B CAp disks, which were uniaxially pressed at 98MPa and sintered at temperatures of 600 to 700 ºC, showed single crystalline phase and a high relative density of 60-62 % compared to the stoichiometric density of 3.16g/cm3 of hydroxyapatite (HAp). The dissolution rate of type B CAp disks sintered at 650 ºC was 3.5 times faster than that of HAp disks at 650 ºC. These results indicate that the Type B CAp sintered disks show potential use as a biodegradable material for artificial bone.


1996 ◽  
Vol 30 (5) ◽  
pp. 1614-1617 ◽  
Author(s):  
Scott E. Fendorf ◽  
Guangchao Li

2010 ◽  
Vol 1277 ◽  
Author(s):  
Ricardo Acosta Ortiz ◽  
Antelmo Yasser Ruiz Martinez ◽  
Aida E García Valdez ◽  
María Lydia Berlanga Duarte

A novel biopolymer derived from diallyl sucrose (A2S) and dithiotreitol (DTT) was prepared by means of Thiol-Ene Photopolymerization. A2S was prepared by alkylating the sucrose with allyl bromide, using water as solvent. After purification by column chromatography, a fraction (F2A2S) with 94% diallyl sucrose (A2S), 4 % of triallyl sucrose (A3S) and 2 % of monoallyl sucrose (A1S) was obtained. This fraction was subsequently photopolymerized with Dithiothreitol (DTT) which is a difunctional thiol. Kinetics of photopolymerization were determined by means of Real-Time Infrared spectroscopy. It was found that the photocurable formulation with DTT and F2A2S, polymerized rapidly in the presence and absence of a photoinitiator, at low intensities of UV light. After bulk polymerization, a flexible material with high elastic modulus and a Tg of 30 °C was obtained. Besides, the polymer displayed moderate water absorbance properties as a result of the presence of multiple hydroxyl groups. This property was pH dependent with maximum absorbance at pH=14. The polymer degraded rapidly under acidic conditions


Toxins ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 662
Author(s):  
Enjie Diao ◽  
Kun Ma ◽  
Hui Zhang ◽  
Peng Xie ◽  
Shiquan Qian ◽  
...  

The thermal stability and degradation kinetics of patulin (PAT, 10 μmol/L) in pH 3.5 of phosphoric-citric acid buffer solutions in the absence and presence of cysteine (CYS, 30 μmol/L) were investigated at temperatures ranging from 90 to 150 °C. The zero-, first-, and second-order models and the Weibull model were used to fit the degradation process of patulin. Both the first-order kinetic model and Weibull model better described the degradation of patulin in the presence of cysteine while it was complexed to simulate them in the absence of cysteine with various models at different temperatures based on the correlation coefficients (R2 > 0.90). At the same reaction time, cysteine and temperature significantly affected the degradation efficiency of patulin in highly acidic conditions (p < 0.01). The rate constants (kT) for patulin degradation with cysteine (0.0036–0.3200 μg/L·min) were far more than those of treatments without cysteine (0.0012–0.1614 μg/L·min), and the activation energy (Ea = 43.89 kJ/mol) was far less than that of treatment without cysteine (61.74 kJ/mol). Increasing temperature could obviously improve the degradation efficiency of patulin, regardless of the presence of cysteine. Thus, both cysteine and high temperature decreased the stability of patulin in highly acidic conditions and improved its degradation efficiency, which could be applied to guide the detoxification of patulin by cysteine in the juice processing industry.


Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5698
Author(s):  
Ana Frangolho ◽  
Bruno E. Correia ◽  
Daniela C. Vaz ◽  
Zaida L. Almeida ◽  
Rui M. M. Brito

One of the molecular hallmarks of amyloidoses is ordered protein aggregation involving the initial formation of soluble protein oligomers that eventually grow into insoluble fibrils. The identification and characterization of molecular species critical for amyloid fibril formation and disease development have been the focus of intense analysis in the literature. Here, using photo-induced cross-linking of unmodified proteins (PICUP), we studied the early stages of oligomerization of human transthyretin (TTR), a plasma protein involved in amyloid diseases (ATTR amyloidosis) with multiple clinical manifestations. Upon comparison, the oligomerization processes of wild-type TTR (TTRwt) and several TTR variants (TTRV30M, TTRL55P, and TTRT119M) clearly show distinct oligomerization kinetics for the amyloidogenic variants but a similar oligomerization mechanism. The oligomerization kinetics of the TTR amyloidogenic variants under analysis showed a good correlation with their amyloidogenic potential, with the most amyloidogenic variants aggregating faster (TTRL55P > TTRV30M > TTRwt). Moreover, the early stage oligomerization mechanism for these variants involves stepwise addition of monomeric units to the growing oligomer. A completely different behavior was observed for the nonamyloidogenic TTRT119M variant, which does not form oligomers in the same acidic conditions and even for longer incubation times. Thorough characterization of the initial steps of TTR oligomerization is critical for better understanding the origin of ATTR cytotoxicity and developing novel therapeutic strategies for the treatment of ATTR amyloidosis.


1971 ◽  
Vol 49 (17) ◽  
pp. 2763-2769 ◽  
Author(s):  
Donald G. Lee ◽  
Udo A. Spitzer

The kinetics of the Oxidation of several sodium p-alkylbenzenesulfonates by aqueous dichromate have been studied under slightly acidic conditions (pH = 7.0 to 5.4). The results indicate that the only active oxidant under these conditions is the acid chromate ion, HCrO4−, and that the reaction probably involves a free radical process.


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