218 research outputs found
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
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
Sorption recovery of metal ions from aqueous solution using humus-boehmite complex
286-292Humic acid (HA) was immobilized on
boehmite (AlOOH) by batch equilibration. Removal of Pb(II), Hg(II) and Cd(II)
from aqueous solution was studied using the batch equilibrium method.
Experiments were earned out as a function of pH and concentration of
metal ions. It was shown that the maximum adsorption of 96.7 % for Pb(II)
occurred at an optimum pH
of 5.5 whereas the maximum adsorption of
91.7% for Hg(II) and 80.8% for Cd(II) was observed at pH 6.0. The adsorption
of metal ion proceeds predominently by the cation-exchange mechanism. Adsorption
isothermal data could be interpreted
by the
Langmuir and Freundlich isotherm equations. Langmuir and Freundlich constants have
been determined . Adsorption experiments were carried
out to investigate the competitive effect on the uptake of metal ions from binary
mixtures. Sheindorf -Rebhun - Sheintuch (SRS) model was used to study the competitive
interactions for the adsorption of Pb-Hg, Pb-Cd and Cd-Hg mixtures by the
adsorbent
Adsorption Characteristics of Hg(II) on Humus-Kaolin Complex: Kinetics and Equilibrium
807-814The kinetics
and equilibrium of the adsorption of Hg(II) by humic acid coated kaolin (HA-kaolin),
a synthetic soil , are studied. The parameters studied are: pH, initial metal ion
concentration, particle size of the HA-kaolin and temperature. The uptake of Hg(II)
increases as the pH is increased and reaches a maximum of 82.8% for the initial
concentration of 10 mg/L at pH 9.0. The applicability of external mass transfer
and intraparticle mass transfer diffusion models has been investigated. The
kinetic parameters such as mass transfer coefficient, diffusion coefficient and
intraparticle rate constant as a function of initial metal concentration, particle
size of the solid and temperature have been calculated for predicting the nature
of adsorption. The intraparticle diffusion of metal ions through pores in the HA-kaolin
is found to be the main rate limiting step. Temperature dependence indicates the
endothermic nature of the process. The significance of the two linear relationships
obtained by plotting the data according to the conventional Langmuir equation is
discussed in terms of the binding energies of the two population sites involved
which have a widely differing affinity for Hg(II) ions
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
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
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