Statistical Modeling and Kinetic Studies on the Adsorption of Reactive Red 2 by a Low-Cost Adsorbent: Grape Waste-Based Activated Carbon Using Sulfuric Acid Activator-Assisted Thermal Activation

The efficiency of activated carbon produced from grape waste as a low-cost, nontoxic, and available adsorbent to remove Reactive Red 2 from aqueous solution has been investigated. The prepared activated carbon has been characterized by FTIR, SEM, and BET. The results of characterization indicate the successful conversion of grape waste into mesoporous AC with desirable surface area consist of different functional groups. The results of statistical modeling displayed high R 2 value of 0.97% for dye removal that shows the developed model has acceptable accuracy. The effect of independent variables indicated that the highest adsorption (96.83%) obtained at pH 3, adsorbent dosage of 12.25 g/L, and initial dye concentration of 100 mg/L when the adsorption time was 90 min. The results of isotherms modeling showed that the data fit well with the Langmuir (type II). The kinetic studies using pseudofirst-order and pseudosecond-order models pointed out that the type (I) of pseudosecond-order kinetic model provided the best fit to the adsorption data. Parameters of thermodynamics including Gibbs energy ( Δ G ° ) and k o were calculated. The values of Δ G ° indicated that the dye adsorption of RR2 is spontaneous. The agricultural wastes due to special points such as low-cost, availability, and high ability to produce an adsorbent with high efficiency to remove dye can be proposed for water and wastewater treatment.

Adsorption behaviors of (–)-epigallocatechin gallate and caffeine on macroporous adsorption resins functionalized with carbazole and N-methylimidazole

Purpose The purpose of this study is to focus on the preparation of macroporous adsorption resins (MARs) functionalized with carbazole and N-methylimidazole, and adsorption behaviors of (–)-epigallocatechin gallate (EGCG) and caffeine (CAF) on the functionalized MARs. Design/methodology/approach Based on the Friedel–Crafts and amination reactions, novel MARs functionalized with carbazole and N-methylimidazole were synthesized and characterized by the BET method. Accordingly, adsorption behaviors and structure-activity relationships for EGCG and CAF were studied in detail. Findings The results showed that pseudosecond-order kinetic model was provided with a better correlation for the adsorption of EGCG and CAF onto L-1 and L-2, and pseudofirst-order kinetic model was the most suitable model to illustrate the adsorption process for EGCG and CAF on L-3. The result indicated that Langmuir, Freundlich, Temkin–Pyzhev and Dubinin–Radushkevich isotherms all could better illustrate the adsorption processes of EGCG and CAF on L-1, L-2 and L-3. Practical implications This study provides theoretical guidance and technical support for the efficient separation and purification of EGCG and CAF from waste tea leaves by MARs on a large scale. In addition, the results showed that this novel MARs would provide useful help and be used in large-scale production of active ingredients from natural products in the industry and other fields. Originality/value Adsorption kinetic models such as pseudofirst-order, pseudosecond-order and intra-particle diffusion kinetic models, and adsorption isotherm models such as Langmuir, Freundlich, Temkin–Pyzhev and Dubinin–Radushkevich isotherms models were adopted to illustrate the adsorption mechanisms of EGCG and CAF. The main driving forces for MARs with no functional groups were pore sieving effects, p–p conjugation effects and hydrophobic interactions, and the other significant driving forces for MARs functionalized with carbazole and N-methylimidazole were electrostatic interactions, ion-dipole and hydrogen bonding interactions. This study might provide scientific references and useful help for large-scale separating and enriching active ingredients in natural products using the technology of MARs with special functional groups.

Investigation of Adsorption of Cobalt-phthalocyanine from Aqueous Waste Stream Using UVM-7/Ag

The effect adsorption of cobalt-phthalocyanine-3,4’,4”,4”’- tetrasulfonicacid tetrasodium salt [Co(tsPc)-4•4Na＋] onto UVM-7/Ag mesoporous material was investigated. In addition, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nitrogen adsorptiondesorption measurement were used to examine the morphology and the microstructure of the obtained composite. Various parameters including solution adsorbent dosage, contact time, initial dye concentration and temperature were systematically studied. Equilibrium data fitted well the Langmuir models; moreover, the fitness suggests that the adsorption be monolayer and physical in nature. Kinetic studies showed that the adsorption process could be better described by the Lagergren pseudosecond- order models. Thermodynamic constant values (ΔG < 0, ΔH< 0 and ΔS< 0) demonstrated that the adsorption reactions of Co(tspc)-4 onto UVM-7/Ag were feasible, spontaneous, and exothermic under the examined conditions.

Kinetics of CO2 Adsorption on Microwave Palm Shell Activated Carbon

Activated carbon was prepared from palm shell by pyrolysis followed by K2CO3 assisted microwave heating. Effects of temperature on adsorption capability and kinetics of the sorbent towards CO2 adsorption was also studied. The results indicated that, the amount CO2 adsorbed decrease as the adsorption temperature increases. The kinetic data were obtained using a static volumetric method at 303.15, 343.15, 378.15, and 443.15 K and at pressures up to 4 bar. The kinetics of CO2 adsorption on the activated carbons was examined using the pseudofirst-order equation and pseudosecond-order equations. Weber and Morris intraparticle diffusion model was applied to examine the mechanism of the adsorption system. Lowest CO2 uptake recorded was 0.3 mmol/g at 443.15 K and 0.5 bar while the highest was 7.45mmol/g obtained at 303.15 K and 4 bar. The kinetics followed pseudosecond-order model. Pore diffusion is not the sole rate diffusion mechanism.

Recovery of Ga(III) by Raw and Alkali Treated Citrus limetta Peels

Alkali treated Citrus limetta peels were used for recovery of Ga(III) from its aqueous solution. The raw and alkali treated peels were characterized for functional groups. The efficiency of adsorption increased from 47.62 mg/g for raw peels to 83.33 mg/g for alkali treated peels. Between pH 1 and 3, the adsorption increased and thereafter decreased drastically. The adsorption followed pseudosecond order kinetics and Langmuir isotherm gave the best fit for the experimental data. Desorption studies showed 95.28% desorption after 3 cycles for raw peels while it was 89.51% for alkali treated peels. Simulated Bayer liquor showed 39.57% adsorption for gallium ions on raw peels which was enhanced to 41.13% for alkali treated peels.

Adsorption of Hg(II) from Aqueous Solution Using Adulsa (Justicia adhatoda) Leaves Powder: Kinetic and Equilibrium Studies

The ability of Adulsa leaves powder (ALP) to adsorb Hg(II) from aqueous solutions has been investigated through batch experiments. The ALP biomass was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The experimental parameters that were investigated in this study included pH, adsorbent dosage, and effect of contact time along with initial metal ion concentration. The adsorption process was relatively fast, and equilibrium was achieved after 40 min of contact time. The maximum removal of Hg(II), 97.5% was observed at pH 6. The adsorption data were correlated with Langmuir, Freundlich, and Temkin isotherms. Isotherms results were amply fitted by the Langmuir model determining a monolayer maximum adsorption capacity (qm) of ALP biomass equal to 107.5 mg g−1and suggesting a functional group-limited sorption process. The kinetic process of Hg(II) adsorption onto ALP biomass was tested by applying pseudofirst-order, pseudosecond-order, Elovich, and intraparticle-diffusion models to correlate the experimental data and to determine the kinetic parameters. It was found that the pseudosecond order kinetic model for Hg(II) adsorption fitted very well. The rate determining step is described by intraparticle diffusion model. These studies considered the possibility of using Adulsa plant leaves biomass as an inexpensive, efficient, and environmentally safe adsorbent for the treatment of Hg(II) contaminated wastewaters.