4 research outputs found

    Production of Biodiesel by Esterification of Stearic Acid over Aminophosphonic Acid Resin D418

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    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)

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    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

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    Thiourea-containing silica gel hydrid materials (HO-SG-GPTS-TS and HE-SG-GPTS- TS) were prepared by homogeneous and heterogeneous methods for Hg­(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 Hg­(II) in the binary system contains Pb­(II), Ni­(II), and Co­(II)

    Synthesis of Silica-Gel-Supported Sulfur-Capped PAMAM Dendrimers for Efficient Hg(II) Adsorption: Experimental and DFT Study

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    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 Hg­(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 Hg­(II) from binary systems containing Hg­(II) with Ni­(II), Cd­(II), Fe­(III), and Zn­(II). DFT calculations revealed that G0-MITC interacts with Hg­(II) through the S atom in a monocoordinated manner, whereas G1.0-MITC behaves as a pentadentate ligand to coordinate with Hg­(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 Hg­(II) was found to occur during the adsorption process
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