Research progress in the removal of heavy metals by modified chitosan

Chitosan and its modifiers have been widely studied for their good biocompatibility and excellent adsorption properties for heavy metal ions. The synthesis and application of modified chitosan, the effects of process variables (such as pH, amount of adsorbent, temperature, contact time, etc.), adsorption kinetics, thermodynamics and the adsorption mechanism on the removal of heavy metal ions are reviewed. The purpose is to provide the latest information about chitosan as adsorbent and to promote the synthesis of modified chitosan and its application in the removal of heavy metals.

Synthesis, Characterizations and Multifunctional Activities of New Thiourea-Based Non-Ionic Surfactants

Six new thiourea-based non-ionic surfactants were prepared from easily existing raw resources in good yield name 1-sec-butyl-3-dodecanoylthiourea, 1-dodecanoyl-3-phenylthiourea, 1,1-dibutyl-3-dodecanoylthiourea, 3-dodecanoyl-1, 1-diphenylthiourea, 1-cyclohexyl-3-dodecanoylthiourea and 1-butyl-3-dodecanoylthiourea. The structural chemistry of these compounds was studied by multinuclear magnetic resonance (1H, 13C), Infrared spectroscopy and UV-Visible spectrophotometry techniques. Their solubility varies according to temperature. They show a low solubility, which increases with the temperature of the water. However, they are not stable. The are soluble in organic solvent like ethanol. These molecules possess a low critical micelle concentration and due to this it shows that they are moderately hydrophobic. These molecules were studied regarding their antimicrobial activities and their antifungal and antibacterial efficiency was tested against five microoganism strains. In all cases, the new compounds show a significant inhibition growth against the tested five bacterial and fungal strains. Due to these behaviors they can be used as future candidates in cleaning as well as in agriculture features. The corrosion inhibition behavior was also studied using chromium and aluminum metals.

Solvent-Free Acetalization of Glycerol with n-Octanal using Combined Brønsted Acid-Surfactant Catalyst

Glycerol, derived from biodiesel production, is a renewable feedstock for the production of value-added chemicals. Herein, we report an investigation of the acetalization of glycerol with n-octanal by homogeneous acid catalysis in the absence of a solvent, using p-dodecylbenzenesulfonic acid, p-toluenesulfonic acid, and sulfuric acid, respectively, as catalysts. p-Dodecylbenzenesulfonic acid, a surfactant-type Brønsted acid, proved to be an excellent catalyst capable of efficiently promoting the reaction under solvent-free conditions, and the yields of glycerol acetals reached 99% under the optimal conditions. The distribution of five- and six-membered cyclic acetal regioisomers varied depending on the reaction time and temperature. Moreover, the amphiphilic properties of the products, with different ratios of five- to six-membered cyclic acetals, have been evaluated by surface tension measurements.

Synthesis and Spectrophotometric Study of Toxic Metals Extraction by Novel Thio-Based Non-Ionic Surfactant

A new thio-based non-ionic surfactant 1-(3-chlorophenyl)-3-te-tradecanoylthiourea has been synthesized from potassium thiocyanate, tetradecanoyl chloride and 3-chloroanaline. The purity of the compound was characterized by techniques like 1H NMR, 13C NMR, and FT-IR. The compound was used to detect the toxic metals like copper, mercury and manganese by using UV-Visible spectrophotometric technique. The compound is able to act as a ligand as well to form micelles. Due to this the compound extracts these toxic metals in form of solubilization and complexation. The extracted metals settle down to the bottom in a water tank. The visible change in color with time proves the interaction of the compound with the metals. The compound having carbonyl as well as sulfur groups have soft corner to metal for complexation. This will be used to remove toxic metals from polluted soil and soft drinking surface and underground water. The surfactant is easily synthesized, very economical and environmentally acceptable. The CMC of the surfactant is also determined.

Methanesulfonic Acid as a More Efficient Catalyst for the Synthesis of Lauraldehyde Glycerol Acetal

The purpose of this paper is to describe a more efficient catalyst for the synthesis of lauraldehyde glycerol acetal. Catalytic effect of methane sulfonic acid and p-toluenesulfonic acid were compared. With a mixture of 0.67 wt.% methanesulfonic acid in relation to lauraldehyde, equimolar amounts of glycerol and lauraldehyde being stirred at 110 °C for 2.5 h, the yield of the product was 76.32 %. When p-toluenesulfonic acid was used, the amount of the catalyst was 0.91 wt.% and the yield of the product was 62.91 % after reacting for 2.5 h at 120 °C. The result reveals that methane sulfonic acid is more efficient. Surface tension measurements showed that critical micelle concentration of the product catalyzed by methanesulfonic acid was 5.33 × 10−5 mol · L−1, and at this point the surface tension could achieve about 24 mN m−1.

Combination of best promoter and micellar catalyst for chromic acid oxidation of 1-butanol to 1-butanal in aqueous media at room temperature

In aqueous acidic media, picolinic acid, 2,2'-bipyridine and 1,10-phenanthroline promoted Cr(VI) oxidation of 1-butanol produces 1-butanal. 1-butanal is separated from mixture by fractional distillation. The anionic surfactant (SDS) and neutral surfactant (TX-100) accelerate the process while the cationic surfactant (CPC) retards the reaction. Combination of bipy and SDS is the best choice for chromic acid oxidation of 1-butanol to 1-butanal in aqueous media.

Micellar Catalysis of Chromic Acid Oxidation of Methionine to Industrially Important Methylthiol in Aqueous Media at Room Temperature

Oxidation of organic molecule by metal is very important. Selective oxidants require non aqueous media, which is toxic and hazardous. L-methionine is oxidized to industrially important methyl thiol in micellar media by chromic acid. The overall reaction follows a first order dependency on substrate and hexavalent chromium and second order dependency on hydrogen ion. Here, reverse micelle formation is observed. TX-100 increases the rate where as SDS retards the rate of oxidation.

Micellar Catalysis on 1,10-Phenanthroline Promoted Chromic Acid Oxidation of Glycerol in Aqueous Media

On pseudo-first order conditions, the monomeric species of Cr(VI) was found to be kinetically active in the absence of phenanthroline (phen) whereas in the phen-promoted path, the Cr(VI)-phen complex undergoes a nucleophilic attack by glycerol to form a ternary complex which subsequently experience a redox decomposition leading to glyceraldehydes and Cr(III)-phen complex. The effect of the cationic surfactant, cetyl pyridinium chloride (CPC); anionic surfactant, sodium dodecyl sulphate (SDS) and nonionic surfactant, triton X-100 (TX-100) on the unpromoted and phen-promoted path have been studied. Micellar effects have been explained by considering the preferential partitioning of reactants between the micellar and aqueous phase.

Micellar Catalysis on Pentavalent Vanadium Ion Oxidation of Ethanol in Aqueous Acid Media

Vanadium(V) oxidation of ethanol follows a first order dependency on the concentration of ethanol, vanadium(V), H+ and HSO4 –. These observations remain unaltered in the presence of externally added surfactants. The effect of the cationic surfactant (i.e., N-cetylpyridinium chloride [CPC]), anionic surfactant (i.e., sodium dodecyl sulphate [SDS]) and neutral surfactant (i.e., Triton X-100 [TX-100]) has been studied. CPC inhibits the reactions, whereas SDS and TX-100 accelerate the reaction to different extents. Observed effects have been justified by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. SDS and TX-100 can be used as catalysts in the production of acetaldehyde from ethanol.

Kinetic Studies of Glutamic Acid Oxidation by Hexavalent Chromium in Presence of Surfactants

Hexavalent chromium is a widespread environmental contaminant and a known human carcinogen. It is a very important to remove toxic Cr(VI) from industrial waste water. In human body Cr(VI) is reduced to Cr(III). Effective bio-molecule present in body contains a number of different functional groups. Kinetics of reduction of Cr(VI) by an important amino acid, glutamic acid in micellar media have been studied spectrophotometrically. Micellar media is a testing enviroment to establish the mechanistic paths of reduction of Cr(VI) to Cr(III). The catalyst and suitable surfactants enhance the reduction of Cr(VI).