Active Sites Of Adsorbent Research Articles

Photomodulation on Active Sites of Adsorbents: Controllable Adsorption Processes with Improved Efficiency.

Adsorption is a widely applied technique in producing high-purity chemicals with advantages of low energy consumption, high selectivity, and mild operating conditions. However, traditional adsorbents have inflexible properties and suffer from the trade-off between selective adsorption and efficient desorption. Recently, the emerging photoresponsive adsorbents have provided new avenues for adsorption techniques. Active sites of photoresponsive adsorbents can be regulated through steric hindrance or tunable adsorbent-adsorbate interactions. Therefore, variation in adsorptive capacity is able to readily achieve through photomodulation, and the corresponding adsorption/desorption cycles are energy-saving. This concept mainly summarizes recent efforts on the fabrication and application of photoresponsive adsorbents with tunable active sites. Also, the future opportunities and critical challenges of photoregulation on adsorptive sites are presented.

Evaluation modified luffa with silver nanoparticles (LF/AgNPs) for removal of a nonsteroidal anti-inflammatory (IBUPROFEN) from aqueous media

This study has investigated luffa as a natural adsorbent modified with silver nanoparticles to sequestrate ibuprofen from aqueous media. Adsorption ibuprofen as an environmental pollutant from aqueous media was studied by various factors such as agitation type, pH, initial drug concentration, contact time, agitation rate, and adsorbent dosage. The optimized experimental parameters were achieved by a one-at-a-time method in 60 min employing vortex in pH = 5, initial concentration of 200 µg/mL, and adsorbent dosage of 25 mg. Isotherms were fitted best to the Freundlich model. Kinetics shows that the adsorption of the drug follows a pseudo-second-order model. According to the obtained results, the adsorption capacity of the prepared adsorbate was 71 mg/g, and 92% of the ibuprofen was removed in the aqueous solutions under optimal conditions. Due to the modification of luffa by silver nanoparticle, the surface charge has been changed and also active sites of adsorbent has been increased. Consequences, π-metal interaction, hydrogen bonding, electrostatic interactions and π-π stacking were involved in the advancement the adsorption mechanism. The results confirmed that the modified luffa is a suitable adsorbent for removing ibuprofen from aqueous solutions.

Lead ferrite-activated carbon magnetic composite for efficient removal of phenol from aqueous solutions: synthesis, characterization, and adsorption studies

A novel lead ferrite-magnetic activated carbon (lead ferrite-MAC) composite was developed using the chemical co-precipitation method. Instrumental analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis were performed to characterize adsorbent. The uptake of phenol from aqueous solutions using the developed adsorbent was compared to that of pristine activated carbon. The maximum adsorption capacity of lead ferrite-MAC composite (145.708 mg/g) was more than that of pristine activated carbon (116.606 mg/g) due to the metal hydroxides coated on activated carbon since they improve the retention of phenol on the available active sites of adsorbent and create an additional electrostatic interaction with the phenol adsorbate. Regarding the high value of the coefficient of determination (R2) and adjusted determination coefficient (R2adj), coupled with the lower values of average relative error (ARE) and minimum squared error (MSE), it can be found that the isothermal data for the lead ferrite-MAC adsorbent were in agreement with the isotherm models of Redlich-Peterson and Langmuir. From the kinetic viewpoint, pseudo-second-order and linear driving force models explained the phenol adsorption data for both adsorbents. The reusability tests for lead ferrite-MAC composite revealed that after six cycles, 85% of the initial adsorption capacity was maintained. The developed adsorbent can be successfully applied to uptake phenol from aqueous solutions.

Black Water Purification by Activated Carbon from Ilalang Weeds (Imperata cylindrica) Adsorbent in Peatland Rural Area

The black water containing humic acid, HA in peat land rural area is a serious issue. This study aims to synthesis of activated carbon, AC from Ilalang Weeds, IW (Imperata cylindrica) as low-cost adsorbent for HA. The success AC synthesis by H3PO4 activator from IW was evidently characterized by Fourier Transform Infra-Red, FTIR and Scanning Electron Microscopy, SEM. The effects of pH solution, initial HA concentration, and contact time were systematically studied to investigate the performance of Activated Carbon from Ilalang Weeds, ACIW. The results showed the increasing of Langmuir monolayer capacity of HA adsorption on carbon from IW before (49.75 mg g-1) and after (56.82 mg g-1) activation process at the pH optimum 6.0. The equilibrium adsorption data fitted with the isotherm model was shifted from multilayer Freundlich model (CIW) into monolayer Langmuir model as the consequences of increasing pore diameter size and active sites intensity. Calculation of adsorption energy by Dubinin-Radushkevich (EDR) model, 0.50 and 2.24 kJ mol-1 for CIW and ACIW, respectively, showed the increasing of physical affinity of HA with the active sites of adsorbent. Adsorption kinetics showed that the adsorption behavior followed the Ho pseudo-second-order kinetic model. The experimental results of this work demonstrate that the ACIW can be used as a promising low-cost adsorbent for HA removal for clean water production in peat land rural area.Â

Surface-Modified Adsorbent from Artocarpus heterophyllus Lam Biomass to Confine Reactive Red 194 in Real and Synthetic Effluents: Kinetics and Equilibrium Study

Chemical activation of Artocarpus heterophyllus Lam (jackfruit peel) via phosphoric acid was focused on this study for the preparation of activated carbon. Carbonization was done at a temperature of 400°C based on the nature of biomass after the impregnation ratio of 1 : 1 (weight of phosphoric acid/weight of raw material). Titanium dioxide was doped on the prepared activated carbon through the sol-gel method. Titanium dioxide doped activated carbon was synthesized to perceive the nature of adsorbents under ambient conditions. Both JPAC and JPAC/TiO2 adsorbents were characterized by the point of zero charges, Fourier transform of infrared spectroscopy, X-ray diffraction spectroscopy, Brunauer-Emmett-Teller analysis, and scanning electron microscopy with energy-dispersive X-ray analysis. The adsorption capacity of Reactive Red 194 (Red 2BN) dye on jackfruit peel activated carbon (JPAC) is 32.271 mg/g, and JPAC/TiO2 is 34.900 mg/g was observed under optimum conditions. Desorption efficiency of JPAC/TiO2 (≥93.4%) is slightly higher compared to JPAC (≥89.2%). Tannery effluents of various parameters were analyzed, and their chemical oxygen demand (COD) values trim down within the permissible limits of JPAC (97%) and JPAC/TiO2 (98%). Experimental data were studied using both two-parameter and three-parameter models of adsorption isotherm, namely, the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Redlich-Peterson, Sips, Toth, and Khan. In which the Langmuir isotherm ([Formula: see text]) best described the experimental data with an optimum monolayer capacity for adsorption capacity of 49.7 mg/g at 323 K on Red 2BN molecules. A proposed scheme of Red 2BN molecules on the active sites of adsorbents was illustrated. Regeneration of spent carbons was studied through different cycles of the run.

Synthesis of nanoadsorbent entailed mesoporous organosilica for decontamination of methylene blue and methyl orange from water

ABSTRACT Water, being a universal solvent, is contaminated by highly toxic pollutants, which is alarming for life on this planet. However, eco-friendly human efforts are constantly trying to overcome this problem. In continuation of these efforts, the present study reported the synthesis of template-supported nanoadsorbents consisting of mesoporous organosilica (MPOS) through poly-condensation of organic (3-methacryloxypropyltrimethoxysilane) and inorganic (sodium silicate) silicon precursors. The nanoadsorbent with suitable textural characteristics, heat-resistant competency and highly porous nature provided a good platform for achieving an excellent performance to remove methylene blue (MB) and methyl orange (MO) from water. Due to easy handling and efficient adsorption capacity, the MPOS nanoadsorbent shows 93.1% and 66.7% adsorptions of MB and MO, respectively. The intra-particle diffusion kinetic model of synthesised materials explained high surface interactions of adsorbate on active sites of adsorbent, which also support possible chemisorption. The MPOS exhibited adsorption capacities of 57.58 mg/g for MB and 56.62 mg/g for MO by using the multilayered sorption mechanism. Reusability of MPOS is also checked up to file cycles and the results indicate the minute decline in the adsorption proficiency of regenerated MPOS. An eco-friendly synthetic approach, efficient exclusion of MB and MO and better regain results make these MPOS a competent nanoadsorbent for water decontamination.

The combined chemical and mechanical modifications of cigarette: a novel methodology to reduce harmful effects

Without hindering the taste, making a cigarette less harmful by reducing the percentage of toxic and carcinogenic compounds in the smoke of the cigarette is a challenging task for the current generation of researchers. In the current work, by implementing mechanical, chemical and combined modification techniques, the above stated is tried to mitigate. In addition to the above, the optimum suction pressure, burning time and the number of puffing are also determined. Mechanical modification technique considers filter to cigarette ratio and filter design as the controlling parameters. The mathematical calculation reveals that puffing should stop when the cigarette length reaches 0.15 times of its original length. Furthermore, it is also identified that the concentrations of suspended solids and droplets in the smoke decrease significantly (separation efficiency = 56.81%) if the cigarette to filter ratio is maintained at 2.32. In case of chemical modification, by using various types of adsorbents such as charcoal and Zeolite 13X, the harmful effects are further reduced. These processes depict significant reduction in harmful effect (separation efficiency up to 62.1%) by showing the decrement in the suspended solids and droplets in the smoke due to the adsorption on the active sites of adsorbents. In case of combined modification, the achieved separation efficiency is 66.51%. For the experimentation, an experimental setup fitted with artificial lungs was used.

Adsorption removal of Cr(VI) by isomeric FeOOH.

The aim of this work is to study the performances of isomeric α-, β-, and γ-FeOOH (goethite, akaganéite and lepidocrocite, including five samples named as Gth1 and Gth2, Aka1 and Aka2, and Lep, respectively) for removing hexavalent chromium (Cr(VI)) from aqueous solutions. The adsorption mechanisms were explored by kinetic and isothermal experiments. Adsorption efficiencies under the different pH values, anions, and the levels of adsorbate and adsorbent were also measured. Results showed that the Cr(VI) adsorption by isomeric FeOOH could be best described by pseudo-second-order kinetic model. The processes of Cr(VI) isothermal adsorption could be greatly fitted by the Langmuir and Freundlich equations with the high correlation coefficients of R2 (>0.92). Also, there were the optimum pH values of 3.0-8.0 for FeOOH to adsorb Cr(VI), and their adsorption capacities were tightly related with the active sites of adsorbents. Cr(VI) adsorptions by these adsorbents were easily influenced by H2PO4 -, and then SO4 2-, while there were little effects by Cl-, CO3 2- and NO3 -. These obtained results could provide a potentially theoretical evidence for isomeric FeOOH materials applied in the engineering treatment of the polluted chromate-rich waters.

Iron-doped chitosan microsphere for As(III) adsorption in aqueous solution: Kinetic, isotherm and thermodynamic studies

Iron-doped chitosan microsphere was prepared successfully and employed for effective adsorption of As(III). The results showed that the adsorption capacity benefited from the increase of iron content, and the maximum adsorption capacity was achieved at pH=8. According to the study of adsorption kinetics, adsorption rate was controlled by liquid film diffusion at a lower rotational speed, while it was controlled by chemical reaction rate at a higher rotational speed. The Freundlich and Temkin models exhibited a better fit to adsorption isotherm data, which indicated the adsorption of As(III) on iron-doped chitosan microsphere was chemisorption and the active sites of adsorbents were non-uniform distributed. Adsorption process was a spontaneous exothermic reaction because its AG and AH were negative. In presence of cations (Cd2+, Pb2+ or Zn2+) in solution, the iron-doped chitosan microsphere also showed the significant removal of As(III). However, the existence of anions (NO 3 − , SO 4 2− or PO 4 3− ) inhibited the As(III) removal at different level. PO 4 3− showed the most significant side effects on the removal of As(III) by iron-doped chitosan microsphere. The used iron-doped chitosan adsorbent can be effectively regenerated using 1.0 mol·L−1 NaOH solution, and the adsorption efficiency decreased only 15.69% after being reused three times. The results of XPS, FT-IR showed that the adsorption was mainly achieved by the coordination interaction between As (III) and doped Fe in adsorbent.

Study of atrazine adsorption kinetics by using an activated carbon synthesised from water hyacinth

In this work, atrazine, one of the most widely used herbicides in Thailand, was removed from water by activated carbon synthesized from water hyacinth. Before adsorption, 3 types of activated carbons used as adsorbents were prepared by different chemical treatment methods; untreated activated carbon (AC), HCl-treated activated carbon (HCl-AC) and NaOH-treated activated carbon (NaOH-AC). After pyrolysis, NaOH-AC became ash, so it was not suitable for using as an adsorbent. Brunauer-Emmett-Teller (BET) and CHNS methods were used to characterised 2 other adsorbents and the results showed that HCl treatment could improve the surface area and carbon content. This led to the better performance of HCl-AC for removing atrazine from water comparing to AC confirming by the adsorption experiments. In addition, the adsorption kinetics of HCl-AC, the best adsorbent in this research, was investigated by fitting with 4 kinetics models. The results showed that pseudo-second-order was the best kinetics model describing that the atrazine adsorption of HCl-AC was limited by adsorption and 2 active sites of adsorbent were required for adsorbing 1 molecule of atrazine.