Removal Of Trichloroacetic Acid Research Articles

Adsorption of trichloroacetic acid from drinking water using polyethylene terephthalate waste carbon and periwinkle shells–based chitosan

Abstract Toxins are formed because of massive anthropogenic activities, polluting freshwater bodies. Most disinfectants used in water purification produce disinfection by-products (DBPs) such as trichloroacetic acid (TCA). TCA is a strong acid, and TCA uptake could harm gastrointestinal tract tissues or result in systemic acidosis. Activated carbons were investigated to remove TCA from drinking water in this study. Elemental and Energy Dispersive X-ray (EDX) and scanning electron microscope methodologies were employed to characterize the surface morphological features of the activated carbons (SEM). Activated carbons’ chemical functional groups were identified through using Fourier transform-infrared (FT-IR) spectroscopy technique. Using a UV-vis spectrophotometer, the TCA concentrations in water samples were examined at 530 nm. The levels of TCA in raw and conventionally treated water were 0.9900 and 2.8900 mg/L, respectively. The polyethylene terephthalate activated carbon (PETAC), polyethylene terephthalate modified activated carbon (PETMAC), and commercial activated carbon (CAC) gave mean TCA removal efficiencies of 80.80%, 90.90%, and 90.90% for raw water and 95.16%, 96.13%, and 100% for conventionally treated water, respectively. The reusability efficiencies of PETAC and PETMAC were 78.4% and 82.4%, respectively. The PETAC with R 2 = 0.9377 showed that Langmuir model best fit the TCA adsorption in the isotherm models. According to the findings, PETAC was effective at removing TCA from water sources and could be improved by incorporating chitosan.

Degradation of trichloroacetic acid by MOFs-templated CoFe/graphene aerogels in peroxymonosulfate activation

Integrating transition-metal and nitrogen into carbon-based materials have been attracted considerable attention in peroxymonosulfate (PMS) activation, but it is a great challenge to establish strong interactions between metal species and graphene. Here, we established metal–organic frameworks (MOFs)-hydrogels which acted as templates to form a family of FeCo/graphene aerogels (C-FeCo, C-CoMIL and C-FeZIF). The C-FeZIF, which co-doped Fe/Co and nitrogen into graphene aerogel, exhibited the most regular and stable metallic frameworks, the best crystallization and biggest pore sizes; it also showed the highest efficiency and stability in PMS catalysis for trichloroacetic acid (TCAA) degradation among these aerogels. By comparative analysis on different catalysis conditions (including catalyst dosage, PMS concentrations and reaction pH), 1 g/L C-FeZIF with 4 mM of PMS reacting under pH 5 showed to be the optimum conditions with an 81.2% removal of TCAA in 160 min. Meanwhile, the C-FeZIF/PMS system also performed well in TCAA degradation within a wide pH range from 3 to 9. Radical analysis suggested that 1O2 was the main active species produced in the C-FeZIF/PMS system, while both SO4•- and •OH radicals assisted the catalytic process to a certain extent. The synthesis process is environmentally friendly, easy to carry out, safe and stable with no secondary pollution, which could be scaled up easily for catalyst preparation for water treatment.

Insights into co-removal of trichloroacetic acid and bromate by an electroreduction process: Competitive reaction mechanism and enhanced atomic H* stabilization

Electrocatalytic reduction treatment is a promising method for the abatement of oxyanions and chlorinated disinfection by-products. The atomic hydrogen (H*) produced by electroreduction of protons/water is highly reductive, whose stabilization on the cathode surface is pivotal to improve the catalytic efficacy. Here, we prepared a noble metal-free N-doped graphene-Cu (NG-Cu) foam electrode by chemical vapor deposition method, which exhibited a superior electrocatalytic activity towards the reduction of bromate and trichloroacetic acid (TCAA) with rate constants of 0.319 and 0.271 min−1 at −1.2 V, respectively. Bromate has a much higher affinity for the reaction sites than TCAA, dividing TCAA reduction into two stages controlled by the surface active sites and diffusion, respectively. Electron spin resonance analysis and density functional theory computations suggested that the production and stabilization of H* are strengthened by the heteroatoms-doping, leading to the higher contribution of indirect H* reduction for both bromate and TCAA removal at NG-Cu foam cathode. This work provided a promising strategy for boosting indirect H* reduction for electrocatalytic purification processes without using precious metal catalysts.

Synthesis, characterization and mechanism analysis of modified crayfish shell biochar possessed ZnO nanoparticles to remove trichloroacetic acid

Trichloroacetic acid (TCAA), as one of the chlorine disinfection by-products, has three harmful effects of carcinogenesis, teratogenesis and mutagenesis towards human health. At present, several adsorbents have been applied to remove TCAA, and crayfish shell has rarely been served as a feedstock for biochar field. In this experiment, crayfish shell (CFS) biochar was creatively applied to remove TCAA as an adsorbent. The synthesis method was used to produce the ZnO-CFS600 from crayfish shell modified by ZnCl2 solution. The removal efficiency of ZnO-CFS600 was determined by batch sorption. Based on the Langmuir model, the maximum adsorption capacity was 17.8 mg/g, which was a dramatical increase in adsorption compared with previous studies. And the adsorption equilibrium time is about 20 h according to the kinetics experiment. The adsorption of ZnO-CFS600 was affected by anion competitions. Low pH provided positive charge condition to enhance the adsorption capacity and the removal process was endothermic. The specific surface area of ZnO-CFS600 significantly increased compared with the companion unmodified biochar. The SEM images indicated that ZnO-CFS600 had a better pore structure and possessed numerous apparent ZnO nanoparticles. The result of XRF showed that there was an increase of Zn content with decrease of Ca on the CFS600 after modification, which led to the presence of ZnO nanoparticles with the size of 37.8 nm based on XRD analysis. FTIR spectra showed that the functional groups on biochar surface had changed. All these results came to the mechanism of ZnO-CFS600 that the removal of TCAA was mainly by surface adsorption, supplemented by electrostatic attraction. This point was vividly illustrated by the following figure. Conclusions of this study constituted a stepping stone to the potential application of modified crayfish shell biochar as an effective sorbent for TCAA.

Reductive dechlorination of trichloroacetic acid (TCAA) by electrochemical process over Pd-In/Al2O3 catalyst

Electrochemical reduction treatment was found to be a promising method for dechlorination of Trichloroacetic acid (TCAA), and acceleration of electron transfer or enhancement of the concentration of atomic H* significantly improve the electrochemical dechlorination process. Bimetallic Pd-based catalysts have the unique property of simultaneously catalyzing the production of atomic H* and reducing target pollutants. Herein, a bimetallic Pd–In electrocatalyst with atomic ratio of 1:1 was evenly deposited on an Al2O3 substrate, and the bimetallic Pd-In structure was confirmed via X-ray photoelectron spectroscopy (XPS). Electrochemical removal of trichloroacetic acid (TCAA) by the Pd-In/Al2O3 catalyst was performed in a three-dimensional reactor. 94% of TCAA with the initial concentration of 500μgL−1 could be degraded within 30min under a relatively low current density (0.9mAcm−2). In contrast to the presence of refractory intermediates (dichloroacetic acid (DCAA)) found in the Pd/Al2O3 system, TCAA could be thoroughly reduced to monochloroacetic acid (MCAA) using Pd-In/Al2O3 catalysts. According to scavenger experiments, an electron transfer process and atomic H* formation function both existed in the TCAA reduction process, and the enhanced indirect atomic H* reduction process (confirmed by ESR signals) played a chief role in the TCAA removal. Moreover, the synergistic effects of Pd and In were proven to be able to enhance both direct electron transfer and indirect atomic H* formation, indicating a promising prospect for bimetallic electrochemical reduction treatment.

Trichloroacetic acid removal by a reductive spherical cellulose adsorbent

A novel spherical cellulose adsorbent with amide and sulphinate groups was used for a first reduction of trichloroacetic acid(TCAA) and a subsequent adsorption of generated species, haloacetic acids. The removal mechanism involved TCAA reduction by sulphinate groups and the adsorption of the haloacetic acids through electrostatic interaction with amide group. Investigation of product formation and subsequent disappearance reveals that the reduction reactions proceed via sequential hydrogenolysis, and transform to acetate ultimately. Adsorption of haloacetic acids was ascertained by low chloride mass balances(89.3%) and carbon mass balances(75.1%) in solution. The pseudo-first-order rate constant for TCAA degradation was (0.93±0.12) h–1. Batch experiments were conducted to investigate the effect of pH value on the reduction and adsorption process. The results show that the reduction of TCAA by sulphinate groups requires higher pH values while the electrostatic attraction of haloacetic acids by amino group is favorable in more acidic media.

Degradation of trichloroacetic acid by an efficient Fenton/UV/TiO2 hybrid process and investigation of synergetic effect

An efficient hybrid degradation process combined Fenton with TiO2 photocatalytic oxidation for trichloroacetic acid (TCAA) was first investigated, and then the synergetic degradation effect between Fenton reagent and TiO2 photocatalytic oxidation was discussed in this study. The dominant factors, such as dosages of TiO2 and Fe2+, TCAA concentration and pH were researched and optimized. The cooperation effect between Fenton and TiO2 photocatalytic oxidation probably occurred because (1) more OH radicals were produced in the Fe(OH)2+ and H2O2 decomposition reactions irradiated by UV light; and (2) photoinduced electrons voluntarily participated in the reduction from Fe3+ to Fe2+, improving the efficient separation of the photogenerated electrons and holes. Adsorption and degradation were both involved in the removal of TCAA in this hybrid process, and the removal of TCAA followed the Langmuir model and the degradation kinetics accorded with first order degradation kinetics. Toxicity test using a bioluminescent bacterium Photobacterium phosphoreum as the indicator proved that the hybrid process was a safe treatment because the toxicity decreased greatly with the degradation time.

TCAA degradation in ultraviolet (UV) irradiation/hydrogen peroxide (H2O2)/micro-aeration (MCA) combination process

The photochemical degradation of trichloroacetic acid (TCAA) employing ultraviolet (UV) irradiation/hydrogen peroxide (H 2 O 2 )/micro-aeration (MCA) combination process was investigated by varying operational parameters. Relatively slow TCAA degradation was observed during direct UV radiation and H 2 O 2 oxidation, while TCAA cannot be removed by MCA alone. UV/H 2 O 2 /MCA combination process proved to be more effective than UV/H 2 O 2 . With the initial concentration of 55.7 μg I -1 , more than 93.4% of TCAA can be removed within 180 min under UV radiation intensity of 1,048.7 μW cm -2 , H 2 0 2 dosage of 30 mg I -1 and MCA flow rate of 25 I min -1 in neutral conditions. Removal rate of TCAA was sensitive to UV radiation intensity, H 2 O 2 dose and solution pH, but appeared to be slightly influenced by initial TCAA concentration. There was a higher correlation between pseudo-first rate constant k and UV intensity and H 2 O 2 dosage, implying that higher removal capacity can be achieved by improvement of both factors. The newly found trichloroacetamide (TCAcAm), the potential TCAA, was more frangible than TCAA, indicating that TCAA hardly regenerates by hydrolysis of TCAcAm. Finally, a preliminary cost analysis revealed that the UV/H 2 O 2 /MCA process was more cost-effective than the UV/H 2 O 2 process in removal of TCAA from drinking water.

Neuron-derived D-Serine Release Provides a Novel Means to Activate N-Methyl-D-aspartate Receptors

D-serine is a coagonist of N-methyl-D-aspartate (NMDA) receptors that occurs at high levels in the brain. Biosynthesis of D-serine is carried out by serine racemase, which converts L- to D-serine. D-serine has been demonstrated to occur in glial cells, leading to the proposal that astrocytes are the only source of D-serine. We now report significant amounts of serine racemase and D-serine in primary neuronal cultures and neurons in vivo. Several neuronal culture types expressed serine racemase, and D-serine synthesis was comparable with that in glial cultures. Immunohistochemical staining of brain sections with new antibodies revealed the presence of serine racemase and D-serine in neurons. Cortical neurons expressing serine racemase also expressed the NR2a subunit in situ. Neuron-derived D-serine contributes to NMDA receptor activation in cortical neuronal cultures. Degradation of endogenous D-serine by addition of the recombinant enzyme D-serine deaminase diminished NMDA-elicited excitotoxicity. Release of neuronal D-serine was mediated by ionotropic glutamate receptor agonists such as NMDA, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid, and kainate. Removal of either external Ca2+ or Na+ blocked D-serine release. Release of D-serine was mostly through a cytosolic route because it was insensitive to bafilomycin A1, a potent inhibitor of vesicular neurotransmitter uptake. D-serine was also not transported into purified synaptic vesicles under conditions optimal for the uptake of known transmitters. Our results suggest that neurons are a major source of D-serine. Glutamate-induced neuronal D-serine release provides a novel mechanism for activating NMDA receptors by an autocrine or paracrine way.

Studies on the Effect of Food Additives on the Activity of Trypsin, using Cup and Disc Methods

For the purpose of studying the effect of food additives on the activity of trypsin, the cup and disc methods were applied. Eight kinds of food additives, i.e., sodium benzoate, sodium dehydroacetate, dulcin, sodium cyclamate, sodium glutamate, glycine, Phloxine and Rose Bengale were tested. In each experimental run, one of these additives was dissolved in 20 ml of 1.5% agar solution (pH 7.6) which contained 0.5% of casein. The casein-agar medium which contained no food additives, was used as the control. These casein-agar solutions were poured into petri-dishes and solidified. Then, diluted trypsinsolutions were added through stainless cup or paper disc to the casein-agar plates in petri-dishes. The dishes were incubated at 37°for 24 hr. After incubation, transparent circles were formed in the plates by the action of trypsin on casein. The outlines of the digested casein circles became distinct by adding 9% trichloroacetic acid. After removal of trichloroacetic acid, the diameters of the circles were measured. The plot of the mean diameters of circles versus logarithm of enzyme concentration became linear. Thus the ratio of the enzyme activity in the presence of each food additive to that of control was calculated. The ratios were very small when dulcin, Phloxine and Rose Bengale were added to the reaction medium. These results showed that these three additives were inhibitory for the tryptic digestion of casein. It was also shown that other five additives had no effect on the activity of trypsin.