Size Selectivity of Anionic and Cationic Dyes Using LDH Modified Adsorbent with Low-Cost Rambutan Peel to Hydrochar

Modification of the layered double hydroxide of CuAl-LDHs by composite with hydrochar (HC) to form CuAl-HC LDH. Material characterization by XRD, FT-IR and SEM analysis was used to prove the success of the modification. The characterization of XRD and FT-IR spectra showed similarities to pure LDH and HC. Selectivity experiments were carried out by mixing malachite green, methylene blue, rhodamine-B, methyl orange, and methyl red to produce the most suitable methyl blue dye for CuAl-LDH, HC and CuAl-HC adsorbents. The effectiveness of CuAl-HC LDH as adsorbent on methylene blue adsorption was tested through several influences such as adsorption isotherm, thermodynamics, and adsorbent regeneration. CuAl-HC LDH adsorption isotherm data shows that the adsorption process tends to follow the Langmuir isotherm model with a maximum adsorption capacity of 175.439 mg/g with a threefold increase compared to pure LDH. The effectiveness of the adsorbent for repeated use reaches five cycles as evidenced by the maximum capacity regeneration data reaching 82.2%, 79.3%, 77.9%, 76.1%, and 75.8%. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Analysis of perspective air preparation network designs in launch complex temperature control systems

The purpose of the research is to perform a comparative analysis of compressed air preparation systems on the basis of moisture content. The article discusses conventional and perspective methods for drying compressed air using condensation, adsorption and membrane technologies. The article considers a temperature control system with the required dew point of minus 25°С at the exit under standard conditions, which corresponds to the dew point temperature plus 3 °С at a pressure of 1.0 MPa, or class 4 according to GOST R ISO 8573-1–2016. The main advantages of using advanced technological drying system designs are described, including the design of a modern drier with a rotary adsorber that can reduce the dew point temperature of compressed air to minus 25…30 °С at 1.0 MPa pressure without any losses on the adsorbent regeneration. This research is the first to analyze the applicability of modern adsorption and membrane modules to the launch complex functions. All the air drying designs were considered in this paper in relation to air temperature control systems based on air refrigerators using the I-d hygrometric chart for variable pressures.

Adsorptive Removal of Cd(II) Ions from Wastewater Using Maleic Anhydride Nanocellulose

In this study, both pristine cellulose nanocrystalline (CNC) and maleic anhydride functionalized cellulose nanocrystalline (MA-CNC) were prepared from the stems of Eichhornia crassipes weed by the sulfuric acid hydrolysis method. The as-prepared adsorbents were characterized by using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and Brunauer–Emmett–Teller (BET) instruments. These materials were applied for the removal of Cd(II) ions from WW. The uptake mechanism was fixed to both Langmuir and Freundlich adsorption isotherms with a maximum Cd(II) ion uptake capability (qmax) of 75.76 and 215.52 mg g−1 by CNC and MA-CNC adsorbents, respectively. Pseudo-second-order (PSO) kinetic model was well fitted to the uptake process. The adsorbent regeneration study was done after desorption of Cd(II) ions from the adsorbent by HCl washing. Results exhibited that the adsorbent was reused for the removal of Cd(II) ions from real WW after successive 13th cycle.

Dye Anionic Removal From Water by Green Synthesized Nannochloropsis Sp.- Cetyltrimethylammonium Bromide Surfactant: Kinetics, Adsorption Isotherm and Adsorbent Regeneration

In this research, biomass modification of Nannochloropsis sp. with surfactant cetyltrimethylammonium bromide (CTAB) through a cation exchange reaction to produce adsorbent Nannochloropsis sp.-cetyltrimethylammonium bromide (AlgN-CTAB). Biomass modification of Nannochloropsis sp. by CTAB has been successfully carried out through confirmation from the analysis data produced by Fourier-transform infrared spectroscopy and scanning electron microscope & energy-dispersive X-ray spectroscopy. AlgN-CTAB adsorbent has been tested for its adsorption ability against anionic dye of methyl orange (MO) in solution by way of a sequence of experiments by the batch method. The optimum conditions for MO removal from the solution occurred at an adsorbent quantity of 0.1 g, pH of 5, and an interaction time of 60 min. MO adsorption kinetics data by AlgN and AlgN-CTAB tended to take the kinetics model of pseudo-second-order (PSO) with PSO rate constant (k2) values of 0.56 and 2.17 g mg-1min-1, serially. The MO adsorption isotherm pattern by AlgN tends to take the Freundlich adsorption isotherm whereas in AlgN-CTAB, it follows the Langmuir and Dubinin-Raduskevich adsorption isotherms (AIML and AIMDR). The results of the adsorption-desorption of MO by AlgN-CTAB with 4 repetition cycles resulted % removal of MO > 80%. The AlgN-CTAB adsorbent can be used repeatedly and is very effective in absorbing MO in solution.

Polydimethyl siloxane/MIL-101 Composites for Enhanced Toluene Adsorption in the Presence of Humidity

<div><b>ABSTRACT</b> <br></div><div><br></div><div> Competition between atmospheric moisture and volatile organic compounds (VOCs) for an adsorbent’s sites can significantly impact its VOC removal efficiency. The development of moisture-tolerant adsorbents is essential to address this issue. A vapor phase deposition process using polydimethylsiloxane (PDMS) has created a hydrophobic form of the highly porous, normally hydrophilic, MOF MIL-101. After optimizing the PDMS vapor deposition time and molecular weights, hydrophobicity index calculations verified the improved hydrophobicity of the coated MOF (MIL-PDMS-Sigma-0.25) over its pristine form. The surface area, pore volume as well as single component vapor adsorption of water and toluene capacities were also preserved, resulting to similar performance to MIL-101. Toluene-water vapor co-adsorption experiments were conducted at 40% RH using two toluene concentrations: 0.5% P/P₀ and 10% P/P₀, mimicking environmental VOC and industrial concentrations, respectively. At 0.5% P/P₀, MIL-PDMS-Sigma-0.25 exhibited 60% higher adsorption capacity and twice the rate of toluene capture relative to pristine MIL-101, as well as a 3-fold higher toluene uptake relative to a commercial activated carbon. Preliminary adsorbent regeneration experiments confirm the stability and performance of MIL-PDMS-Sigma-0.25. Using a simple vapor phase modification, this new MOF-composite material offers superior competitive toluene vapor uptake in humidified real-world conditions at VOC concentrations. </div>

Polydimethyl siloxane/MIL-101 Composites for Enhanced Toluene Adsorption in the Presence of Humidity

<div><b>ABSTRACT</b> <br></div><div><br></div><div> Competition between atmospheric moisture and volatile organic compounds (VOCs) for an adsorbent’s sites can significantly impact its VOC removal efficiency. The development of moisture-tolerant adsorbents is essential to address this issue. A vapor phase deposition process using polydimethylsiloxane (PDMS) has created a hydrophobic form of the highly porous, normally hydrophilic, MOF MIL-101. After optimizing the PDMS vapor deposition time and molecular weights, hydrophobicity index calculations verified the improved hydrophobicity of the coated MOF (MIL-PDMS-Sigma-0.25) over its pristine form. The surface area, pore volume as well as single component vapor adsorption of water and toluene capacities were also preserved, resulting to similar performance to MIL-101. Toluene-water vapor co-adsorption experiments were conducted at 40% RH using two toluene concentrations: 0.5% P/P₀ and 10% P/P₀, mimicking environmental VOC and industrial concentrations, respectively. At 0.5% P/P₀, MIL-PDMS-Sigma-0.25 exhibited 60% higher adsorption capacity and twice the rate of toluene capture relative to pristine MIL-101, as well as a 3-fold higher toluene uptake relative to a commercial activated carbon. Preliminary adsorbent regeneration experiments confirm the stability and performance of MIL-PDMS-Sigma-0.25. Using a simple vapor phase modification, this new MOF-composite material offers superior competitive toluene vapor uptake in humidified real-world conditions at VOC concentrations. </div>

Recovery of Potassium from Incineration Ash of Chicken Dropping (IACD) by Sulphuric Acid Leaching Followed by Adsorption Using Orange Waste Gel

Two types of leaching solution namely; aqua-regia and 1MH2SO4 were investigated for the leaching of K(I) from incineration ash of chicken dropping (IACD), in this study. SOJR and Na(I)-SOJR adsorbents were prepared from orange juice residue for the adsorption of K(I) from IACD leached liquor, which was compared with READF-(PG) and 200CT resin. The characterization of IACD leaching was done in EDX and FTIR spectroscopic techniques. Aqua-regia solution completely dissolved IACD and all the adsorbents. One molar sulphuric acid (1MH2SO4) solution was optimized for effective leaching of K(I) from the IACD sample. SOJR, Na(I)-SOJR, and 200CT adsorbed K(I) from leached liquor whereas K(I) was insignificantly adsorbed onto READF-(PG). The desorption of adsorbed K(I) could be successfully done by H2SO4 solution for recovery and adsorbent regeneration for further usage. From comparisons, Na(I)-SOJR investigated in this study was found to be equally effective with a commercially available cation exchanger (200CT resin). Therefore, a new method of H2SO4 leaching of IACD followed by adsorption using Na(I)-SOJR investigated in this work can be an economic, environmentally benign, and promising technique for the recovery of K(I) ion from leach liquor of IACD.

Removal of diclofenac from aqueous solutions by adsorption on thermo-plasma expanded graphite

The adsorption of diclofenac on thermo-plasma expanded graphite (a commercial product) from water solutions was investigated. The adsorbent material was characterized by SEM, TEM, BET, Raman and X-ray diffraction analyses. Typical diffractogram and Raman spectrum of graphitic material, dimension of 24.02 nm as crystallite dimension and a surface area of 47 m2 g−1 were obtained. The effect of pH on the adsorption capacity was evaluated in the range 1–7 and the adsorption mechanism was described by kinetic and isothermal studies. Pseudo-second order and Dubinin–Radushkevich models agreed with theoretical values of adsorption capacity (i.e. 400 and 433 mg g−1, respectively) and resulted to be the best fit for kinetics and isothermal experimental data. The thermodynamics of the process was evaluated by plotting the adsorption capacity/concentration ratio at the equilibrium as a function of different values of the multiplicative inverse of temperature. Moreover, the adsorbent regeneration was also investigated, comparing two different remediation techniques. Solvent washing performed with NaOH 0.2 M and thermo-treatment carried out by heating in an oven at 105 °C for 2 h and then at 200 °C for 4 h. The thermo-treatment was the best technique to regenerate the adsorbent, ensuring same performance after 4 cycles of use and regeneration.