Effect of template in MCM-41 on the adsorption of aniline from aqueous solution

PANI/MCM-41 adsorption for removal of Cr(VI) ions and its application in enhancing electrokinetic remediation of Cr(VI)-contaminated soil

In this study, a polyaniline/mesoporous silica (PANI/MCM-41) composite material that can be used as a filler for permeable reactive barrier (PRB) was prepared by in situ polymerization. Firstly, the adsorption capacity of PANI/MCM-41 on Cr (VI) in solution was investigated. The results show that the prepared PANI/MCM-41 exhibits a significant Cr (VI) adsorption capacity (~ 340 mg/g), and the adsorption process is more accurately described by the Langmuir isotherm and pseudo-second-order kinetic model. The thermodynamic functions evidenced that the Cr(VI) adsorption was an endothermic spontaneous process. In addition, adsorption-desorption cycle experiments proved the excellent reusability of the material. Subsequently, the material was utilized as a filler in the PRB for the remediation of Cr(VI)-contaminated soil using electrokinetic-permeable reactive barrier (EK-PRB) technology. The results show that compared with traditional electrokinetic remediation, the use of PANI/MCM-41 as an active filler can enlarge the current during remediation and enhance the conductivity of soil, which increases the removal rates of total Cr and Cr(VI) in soil (17.4% and 10.2%).

Electrocatalytic oxidation of aromatic amine (4-aminobiphenyl): Kinetics and transformation products with mechanistic approach

Electrocatalytic oxidation (EO) of carcinogenic 4-aminobiphenyl (4-ABP) aromatic amine was performed using Ti-RuO₂ anodes. Current (I), pH, electrolysis time (t), and 4-ABP initial concentration (C_o ) were selected as EO parameters, and their effects on %4-ABP removal (R₁ ) and energy consumed (R₂ ) were studied. Experimental design, parameters optimization, and their interaction with responses R₁ and R₂ were performed using response surface methodology. At optimized parameters, %TOC removal and 4-BP mineralization current efficiency (%MCE) were assessed to evaluate the potential of Ti/RuO₂ anodes towards 4-ABP mineralization. Simultaneous TOC and 4-ABP degradation kinetics were also studied to evaluate the competition in 4-ABP mineralization and degradation. Further, UPLC-Q-TOF-MS analysis was performed to identify the 4-ABP transformation products during the EO, and a mechanism describing the EO transformation was proposed. At optimum parameters (I = 1.2 A; pH = 4.0; t = 30 min; C_o  = 30 ppm), responses were found to be R₁  = 60.25%; R₂  = 2.49 kWh/g of 4-ABP removed. %TOC removal and %MCE were 52.4% and 34.2%, respectively. PRACTITIONER POINTS: 4-Aminobiphenyl electro-oxidation (EO) was explored using Ti/RuO₂ anode. Achieved 34.2% mineralization current efficiency, 52.4% TOC and 61.3% TKN removal. Three electro-oxidation transformation products of 4-ABP were detected. 4-Aminobiphenyl was found degrading at ≈1.6 times higher rate than TOC A plausible EO transformation pathway and mechanism was proposed.

Potential low-cost carbon-based adsorbent from gold mine tailings for anionic dye removal

In this study, a mesoporous carbon (CMK-3) was successfully synthesized using mesoporous silica (SBA-15) prepared from gold mine tailings (sample C_GMT) for removal of anionic dye from aqueous solution. For comparison, CMK-3 was prepared by the same method from pure silica (sample C_T), and the other CMK-3 sample was prepared by a one-pot route mixing with Pluronic P123 (sample C_P). The effect of the carbonization time on the synthesis of all CMK-3 samples was investigated, and the samples were characterized by X-ray diffraction and N₂ adsorption-desorption. The sample with the highest surface area was chosen as an adsorbent, for each CMK-3 obtained from different methods. Batch adsorption experiments were studied to determine the influence of pH, contact time, and initial dye concentration. The adsorption kinetics obeyed the pseudo-second-order model. All carbon-based adsorbents were observed to be quite effective for the removal of dye with adsorption percentage in the order of C_P > C_T > C_GMT. The maximum adsorption capacities were 188.99 and 204.57 mg·g^-1 for C_T and C_GMT, respectively. The comparative results of all carbon-based adsorbents show that C_GMT can be applied as a low-cost alternative to C_T for dye removal.

Binder-free preparation of ZSM-5@silica beads and their use for organic pollutant removal

Organic structure directing agent (OSDA)- and binder-free preparation of ZSM-5@silica beads and their use for aniline removal.

Aromatic amines equilibrium sorptive interaction with synthesized silica based mesoporous MCM-41: Physicochemical evaluation and isotherm modeling

Present study reports the adsorption of aromatic amine, 4-chloro-o-toluidine (4-COT), onto synthesized mesoporous Mobil Composition of Matter No. 41 (MCM-41) silica nanoparticles, in batch mode. Synthesized MCM-41 was characterized by XRD, BET, FTIR, SEM and TEM analysis. The effects of pH, MCM-41 dose, 4-COT concentration, contact time and temperature were studied, and interaction of 4-COT with the surface of MCM-41 and adsorption process controlling mechanism were investigated. BET analysis of MCM-41 showed 502.77 m² g^-1 of surface area. Kinetic experimental data were well represented by the pseudo-second order kinetic model. Freundlich and Temkin isotherm models well represented the adsorption equilibrium isotherm data.

Adsorption of aniline from aqueous solution using graphene oxide-modified attapulgite composites

Adsorption is an efficient treatment method for aniline removal in water treatment.

Micelles as Soil and Water Decontamination Agents

Contaminated soil and water pose a serious threat to human health and ecosystem. For the treatment of industrial effluents or minimizing their detrimental effects, preventive and remedial approaches must be adopted prior to the occurrence of any severe environmental, health, or safety hazard. Conventional treatment methods of wastewater are insufficient, complicated, and expensive. Therefore, a method that could use environmentally friendly surfactants for the simultaneous removal of both organic and inorganic contaminants from wastewater is deemed a smart approach. Surfactants containing potential donor ligands can coordinate with metal ions, and thus such compounds can be used for the removal of toxic metals and organometallic compounds from aqueous systems. Surfactants form host-guest complexes with the hydrophobic contaminants of water and soil by a mechanism involving the encapsulation of hydrophobes into the self-assembled aggregates (micelles) of surfactants. However, because undefined amounts of surfactants may be released into the aqueous systems, attention must be paid to their own environmental risks as well. Moreover, surfactant remediation methods must be carefully analyzed in the laboratory before field implementation. The use of biosurfactants is the best choice for the removal of water toxins as such surfactants are associated with the characteristics of biodegradability, versatility, recovery, and reuse. This Review is focused on the currently employed surfactant-based soil and wastewater treatment technologies owing to their critical role in the implementation of certain solutions for controlling pollution level, which is necessary to protect human health and ensure the quality standard of the aquatic environment.

Fabrication of mesoporous Al-SBA-15 as a methylene blue capturer via a spontaneous infiltration route

Mesoporous Al-SBA-15 materials were synthesized via a facile solvent-free method and they present much higher MB adsorption capacity than the siliceous SBA-15.

Mesoporous carbon nitride as a metal-free catalyst for the removal of aniline

Metal-free mesoporous carbon nitride exhibited good activity for catalytic removal of aniline owing to the mesoporosity and favorable adsorption sites.

Chemically modified poly(2-hydroxyethyl methacrylate) cryogel for the adsorption of heparin

Various clinical procedures, such as cardiovascular surgery or extracorporeal blood purification, involve systemic anticoagulation using heparin. High concentrations of circulating heparin require neutralization due to possible serious bleeding complications. The intravenous administration of the heparin antagonist protamine sulfate is routinely clinically performed, but is frequently associated with adverse reactions. Therefore, there is a need for a valid and safe alternative to achieve extracorporeal heparin removal from blood or plasma, such as a filter, a matrix, or an adsorbent. Here, we describe the development of a macroporous poly(2-hydroxyethyl methacrylate)-based monolithic cryogel functionalized with l-lysine (pHEMA-lys) and the characterization of its selective heparin adsorption. The maximum binding capacity was quantified in vitro using aqueous and serum solutions under static and dynamic conditions, and fresh human plasma under static conditions. The pHEMA-lys bound 40,500 IU and 32,500 IU heparin/g cryogel at the equilibrium in aqueous solution and 50% serum, respectively. In human plasma spiked with 100 IU/mL of heparin, the binding was still highly efficient (4330 IU/g cryogel after 30 min, i.e., 87% of the initial concentration). The cryogels showed good blood compatibility, as indicated by negligible adsorption of albumin, antithrombin III, and total protein, and may thus be suitable for extracorporeal heparin removal.

Titania/CnTAB Nanoskeleton as adsorbent and photocatalyst for removal of alkylphenols dissolved in water

We report here on the removal of alkylphenols (phenol, 4-n-propylphenol, 4-n-heptylphenol and 4-nonylphenol) dissolved in water using the composite particles of nanocrystalline titania and alkyltrimethylammonium bromide (CnH2n+1N(CH3)3Br, CnTAB; n=12, 14, 16 and 18) (named as TiO2/CnTAB Nanoskeleton) as adsorbents and photocatalysts. In particular, the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton in water was investigated in terms of hydrophobic interaction between alkylphenols and CnTAB, surface area, pore structure and crystal size of TiO2/CnTAB Nanoskeleton. We revealed that CnTAB incorporated in the TiO2/CnTAB Nanoskeleton promotes the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton due to the hydrophobic interaction between alkylphenols and CnTAB. On the other hand, the surface area, pore structure and crystal size of TiO2/CnTAB Nanoskeleton did not affect the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton. We also found that the alkylphenols dissolved in water were completely removed by the combination of adsorption and photocatalytic degradation by the TiO2/CnTAB Nanoskeleton under UV irradiation. These results prove that the TiO2/CnTAB Nanoskeleton acts as in tandem an adsorbent and a photocatalyst for removal of alkylphenols dissolved in water.