Removal of Tannic Acid From Aqueous Solution by Cloud Point Extraction and Investigation of Surfactant Regeneration by Microemulsion Extraction

The aim of this work is the extraction of tannic acid (TA) with two commercial nonionic surfactants, separately: Lutensol ON 30 and Triton X-114 (TX-114).The experimental cloud point extraction results are expressed by four responses to surfactant concentration and temperature variations: extent of TA extraction (E), remaining solute (X s,w) and surfactant (X t,w) concentrations in dilute phase and volume fraction of coacervate (Φc) at equilibrium. An empirical smoothing method was used and the results are represented on three dimensional plots. In optimal conditions, the extraction extent of TA reaches 95 and 87 % using TX-114 and Lutensol ON 30, respectively. Sodium sulfate, cetyltrimethylammonium bromide (CTAB) addition and pH effect are also studied. Finally, the possibility of recycling of the surfactant is proved

Valorisation of Biowastes for the Production of Green Materials Using Chemical Methods

With crude oil reserves dwindling, the hunt for a sustainable alternative feedstock for fuels and materials for our society continues to expand. The biorefinery concept has enjoyed both a surge in popularity and also vocal opposition to the idea of diverting food-grade land and crops for this purpose. The idea of using the inevitable wastes arising from biomass processing, particularly farming and food production, is, therefore, gaining more attention as the feedstock for the biorefinery. For the three main components of biomass—carbohydrates, lipids, and proteins—there are long-established processes for using some of these by-products. However, the recent advances in chemical technologies are expanding both the feedstocks available for processing and the products that be obtained. Herein, this review presents some of the more recent developments in processing these molecules for green materials, as well as case studies that bring these technologies and materials together into final products for applied usage

<span style="font-size:12.0pt;font-family:"Times New Roman","serif"; mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-ansi-language: EN-IN;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Influence of organic ligands on kinetics of adsorption of lead(II) by kaolin under various <i style="mso-bidi-font-style:normal">p</i>H conditions</span>

1029-1034Adsorption of lead(II) from aqueous solution in presence of nitrilotriacetic acid(NTA) and ethylenediaminetetraacetic acid(EDTA) by kaolin has been studied using the batch equilibrium method. The study shows that Pb(II) adsorption by kaolin at different concentrations of NTA and EDTA obeys multiple first-order kinetics. The rate constants of Pb(II) adsorption for both fast and slow processes in presence and absence of organic ligands at different <i style="mso-bidi-font-style: normal">pH values have also been determined. With increase in pH the adsorption of NTA and EDTA decreases. In the absence of organic ligands the rate constants of initial fast process were 18-27 times higher than the slow process in the pH range of 2.0 to 9.0. Maximum adsorption of organic ligands takes place at pH 2.0. NTA and EDTA have a significant promoting effect on the adsorption of Pb on to kaolin at pH 2.0 whereas the ligands have a significant retarding effect on the adsorption at pH 4.0 and 9.0. The kaolin surface carries a net positive charge at pH 2.0, thus negatively charged Pb-NT A or Pb-EDTA complexes can be readily adsorbed. Adsorbed NTA and EDTA at kaolin surface provide new adsorption sites for Pb(II) ions.</span

Adsorption Equilibria of Hg(II) on Clays in Presence of Organic Materials

883-892Adsorption of Hg(II), organic ligands (HA, NTA, EDTA and CDTA) and Hg(II) in the presence of organic ligands on montmorillonite, illite and kaolin from water environment is reported. The maximum adsorption of Hg(II) onto montmorillonite and kaolin lakes place in the pH range 5-10. The maximum removal of Hg(II) by illite is observed at pH 8. The efficiency for the removal of Hg(II) by adsorption is in the order: montmorillonite > illite > kaolin. The adsorption isotherm data follows both the Langmuir and Freundlich isotherm equations. The maximum removal of organic ligands by adsorption is observed at low pH and is in the order: HA >NTA > EDTA > CDTA. The monovalent species of EDT A and CDTA have lower adsorption capacity than divalent species of NTA on the clay surface at pH 3.0. In ligand titration experiments, if the Hg and clay concentrations are kept constant and the ligand concentration is allowed to vary, conditions under which ligand enhances and inhibits Hg adsorption with the solid phase are noted. The experimental equilibrium data for the adsorption of Hg(II) in the presence of ligand at constant L/M ratio are analysed using Langmuir isotherm model. The enhanced uptake of metal in the presence of organic ligands, at least at certain circumstances, may be due to the formation of an adsorbed organic layer on the clay providing new adsorption sites for metal at the surface

Removal of Hg(II) from aqueous solution by sorption on polymerised saw dust

49-54<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-fareast-font-family:"dejavu="" sans";="" mso-bidi-font-family:mangal;mso-bidi-theme-font:minor-bidi;mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The ability of polymerised saw dust to adsorb Hg(II) from water has been carried out. The per cent of Hg(II)adsorbed increased with decrease in initial concentration of Hg(ll), increase in adsorbent dosage and temperature. Maximum accumulation was noted within 4 h and maximum removal (94%) was recorded below 10 mg/L of Hg(II).The process follows a first order rate kinetics with diffusion controlled nature and the data fits the Langmuir adsorption isotherm. Sorbent is effective for the quantitative removal of Hg(II)over the pH range 3.5-8.5. Adsorption rate constants, and thermodynamic parameters were also presented to predict the nature of adsorption. Extraction studies confirmed that most Hg(II)could be released by exposure to 1 MHCl or chelating agent (0.1 M EDTA).</span

Kinetics of Pb(II) adsorption by polyacrylamide grafted sawdust

157-162<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "dejavu="" sans";mso-hansi-theme-font:minor-latin;mso-bidi-font-family:mangal;="" mso-bidi-theme-font:minor-bidi;color:#00000a;mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Lead (ll) removal efficiency of polyacrylamide grafted sawdust has been investigated through la-boratory experiments. Kinetic measurements have been made as a function of solution concentration of Pb(II) ions, pH and temperature. The slow step governing the rate of exchange is diffusion of ions through the exchanger particles. The equilibrium data fit well with the Langmuir isotherms. Thermodynamic parameters were also presented to predict the nature of adsorption. Adsorbent can be regenerated with acid and can then be reused.</span

Adsorption thermodynamics of phosphate on sediments of tropical backwater system

125-132The effect of phosphate concentrations, contact time, pH, diverse ions and temperature on adsorption of phosphate by sediments from retting and non-retting zones have been studied. The percent phosphate adsorbed increased with decrease in initial concentration of phosphate and increase in temperature. The adsorption capacity increased with decrease in pH, being the highest at an initial pH of 3.5. The adsorption isotherms of phosphate follow the Freundlich model and yield 'L' class for retting zone sediments and 'S' class for non-retting sediments. The thermodynamic equilibrium constant (K-0), standard free energy (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees) changes were also being evaluated to predict the nature of adsorption

Effect of NTA and pH on Lead(II) Adsorption by the Hydrous Oxides of Mn, Fe, and A1

145-150The object of this work was to study the influence of nitrilotriacetic acid (NTA) on Pb(II) adsorption by different hydrous oxide gels (MnOOH, FeOOH and AlOOH) at different pH levels. The surface charge density as a function of pH in aqueous solution of NaNO3, NTA and Pb-NTA has been determined. In the presence of NTA the values of zero point charge (pHzpc) for AlOOH, FeOOH and MnOOH were shifted downwards from 9.2 to 8.5, 7.3 to 6.5 and 3.8 to 3.6 respectively. The pHzpc values for AlOOH, FeOOH and MnOOH in the presence of Pb and NTA were found to be 7.3, 6.0, and 3.2 respectively. An empirical relationship has been obtained to predict the pHzpc at any amount of NTA adsorption on AlOOH. The adsorption characteristics of Pb and NTA in presence of each other has been studied. The adsorption of Pb(II) in presence of NTA was greater than NTA adsorption in presence of Pb(II). The maximum adsorption of Pb (II) in presence of NTA occur at a pH range of 3.0-4.0. The oxide surface carries a net positive charge at pH range 3.0-4.0 thus negatively charged Pb-NTA2- complex can be readily adsorbed