4 research outputs found
Production of Biodiesel by Esterification of Stearic Acid over Aminophosphonic Acid Resin D418
Biodiesel production has become a very intense research
field because
of its environmental benefits and the growing interest in finding
new resources and alternatives for conventional fuels. In the present
work, biodiesel production from the esterification of the free fatty
acid stearic acid with ethanol over aminophosphonic acid resin D418
was studied. The effects of experimental factors such as the amount
of D418, reaction temperature, and molar ratio of ethanol to stearic
acid on the conversion ratio were evaluated. Process optimization
using response surface methodology (RSM) was performed, and the interactions
between the operating variables were elucidated. The optimum values
for maximum esterification percentage were obtained by using a Box–Behnken
center-united design with a minimum of experimental work. Moreover,
the kinetics of the esterification catalyzed by D418 was studied,
and the pseudohomogeneous (PH) model was used to simulate the experimental
data
Synthesis of Aminomethylpyridine-Decorated Polyamidoamine Dendrimer/Apple Residue for the Efficient Capture of Cd(II)
Water contamination irritated by Cd(II) brings about
severe damage
to the ecosystem and to human health. The decontamination of Cd(II)
by the adsorption method is a promising technology. Here, we construct
aminomethylpyridine-functionalized polyamidoamine (PAMAM) dendrimer/apple
residue biosorbents (AP-G1.0-AMP and AP-G2.0-AMP) for adsorbing Cd(II)
from aqueous solution. The adsorption behaviors of the biosorbents
for Cd(II) were comprehensively evaluated. The maximum adsorption
capacities of AP-G1.0-AMP and AP-G2.0-AMP for Cd(II) are 1.40 and
1.44 mmol·g–1 at pH 6. The adsorption process
for Cd(II) is swift and can reach equilibrium after 120 min. The film
diffusion process dominates the adsorption kinetics, and a pseudo-second-order
model is appropriate to depict this process. The uptake of Cd(II)
can be promoted by increasing concentration and temperature. The adsorption
isotherm follows the Langmuir model with a chemisorption mechanism.
The biosorbents also display satisfied adsorption for Cd(II) in real
aqueous media. The adsorption mechanism indicates that C–N,
NC, C–O, CONH, N–H, and O–H groups participate
in the adsorption for Cd(II). The biosorbents display a good regeneration
property and can be reused with practical value. The as-prepared biosorbents
show great potential for removing Cd(II) from water solutions with
remarkable significance
Preparation and Characterization of Thiourea-Containing Silica Gel Hybrid Materials for Hg(II) Adsorption
Thiourea-containing
silica gel hydrid materials (HO-SG-GPTS-TS and HE-SG-GPTS- TS) were
prepared by homogeneous and heterogeneous methods for HgÂ(II) adsorption.
Structures of HO-SG-GPTS-TS and HE-SG-GPTS-TS were confirmed by FTIR, <sup>13</sup>C NMR, <sup>29</sup>Si NMR, SEM, TGA, and porous structure
analysis. Homogeneous preparation is demonstrated to be more efficient
than heterogeneous one to load more functional groups and therefore
shows better adsorption property. The optimal adsorption pH was 6
for the adsorbent. Kinetics of adsorption was well fitted by a pseudo-second-order
model and dominated by film diffusion process. The isotherm adsorption
was best described by Langmuir isotherm model and processed by chemical
mechanism. Thermodynamics implied the adsorption was spontaneous and
endothermic. Selective adsorption indicated HO-SG-GPTS-TS exhibited
excellent selectivity for HgÂ(II) in the binary system contains PbÂ(II),
NiÂ(II), and CoÂ(II)
Synthesis of Silica-Gel-Supported Sulfur-Capped PAMAM Dendrimers for Efficient Hg(II) Adsorption: Experimental and DFT Study
A series of silica-gel-supported
sulfur-capped PAMAM dendrimers
(SiO<sub>2</sub>-G0-MITC–SiO<sub>2</sub>-G2.0-MITC) were synthesized
and used for the adsorption of HgÂ(II) from aqueous solution. The optimum
adsorption pH was found to be 6. Adsorption kinetics indicated that
equilibrium can be approached in about 220 min and that the adsorption
capacity increased with increasing generation of sulfur-capped PAMAM
dendrimers. The kinetics of the adsorption process was found to be
controlled by film diffusion and to follow a pseudo-second-order model.
The adsorption isotherms were fitted well by the Langmuir isotherm
model, and adsorption was found to take place by a chemical mechanism.
Thermodynamic analysis demonstrated that the adsorption was a spontaneous,
endothermic, and randomness-increasing process. Adsorption selectivity
experiments showed that SiO<sub>2</sub>-G0-MITC–SiO<sub>2</sub>-G2.0-MITC can selectively adsorb HgÂ(II) from binary systems containing
HgÂ(II) with NiÂ(II), CdÂ(II), FeÂ(III), and ZnÂ(II). DFT calculations
revealed that G0-MITC interacts with HgÂ(II) through the S atom in
a monocoordinated manner, whereas G1.0-MITC behaves as a pentadentate
ligand to coordinate with HgÂ(II) through the N atom of the tertiary
amine group, the O atoms of the amide groups, and the S atoms. Charge
transfer from G0-MITC and G1.0-MITC to HgÂ(II) was found to occur during
the adsorption process