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Mesoporous silica SBA-15 grafted with benzene-1,3,5-triamido-tetraphosphonic acid (SBA-15-BTATPA) was synthesized. After detailed characterization of the material using various analytical instrumentation, it was applied for the recovery of Nd 3+ as a function of the contact time, ion concentration, and pH. The adsorption equilibria and kinetics were also examined. Under the optimal conditions, adsorption equilibrium was reached within 60 min of contact time, and the adsorption capacity of Nd 3+ at room temperature and pH 6 was 129.8 mg g −1 , which was higher than that by other rare earth element (REE) ions tested for comparison (Y 3+ , La 3+ , and Ce 3+ ). The adsorbent showed excellent distribution coefficient for Nd 3+ greater than 1.0 × 10 5 mL/g. The preferential order of adsorption in the ion mixture with equal ion concentrations was Y 3+ >Nd 3+ >Ce 3+ >La 3+ , which followed the sequence of their decreasing atomic size and increasing stability constant. The competing adsorption by transition metal ions, such as Cu 2+ , Ni 2+ , Co 2+ , and Zn 2+ , on the REEs recovery was negligible (<2%). The observed adsorption isotherms could be fitted well to a Langmuir model (correlation factor R 2 > 0.99), whereas the adsorption kinetics could be described satisfactorily by a pseudo second order kinetic model. The material was reusable for up to 5 consecutive times with only a slight decrease in adsorption capacity. [ABSTRACT FROM AUTHOR]

[Display omitted] • KOH was impregnated on rice husk KOH-activated carbon, named as DKOH-AC. • DKOH-AC involved both chemi- and physi-sorption when KOH-AC allowed physi-sorption. • CO 2 adsorption on DKOH-AC followed Freundlich and pseudo second order models. • DKOH-AC adsorbed 2.1 mmol/g in an indoor condition. Relatively high indoor CO 2 concentration (greater than 1000 ppm) has a negative impact on human health. In this work, a cost-effective CO 2 adsorbent (DKOH-AC) was developed by impregnating KOH on rice husk-based KOH activated carbon (KOH-AC, 1439 m2/g). KOH can be successfully loaded on the surface of KOH-AC and significantly changed its surface properties. DKOH-AC still remained a considerable surface area (206 m2/g) and showed a similar S micro /S BET ratio. In-situ FTIR analysis confirmed that the major CO 2 adsorption mechanism of KOH-AC was based on physisorption while that on DKOH-AC involved both chemisorption and physisorption. DKOH-AC showed a higher heat of adsorption (34 ∼ 41 KJ/mol) and gas selectivity (16.6) than these of KOH-AC. KOH-AC quickly reached an adsorption equilibrium (about 50 min) as compared to that of DKOH-AC. In addition, DKOH-AC exhibited an excellent adsorption performance of 2.1 mmol/g for a low concentration of CO 2 (2000 ppm ∼ 500 ppm) under indoor conditions. Both the CO 2 adsorption isotherm on KOH-AC and DKOH-AC well followed the Langmuir and Freundlich models. The CO 2 adsorption kinetics on KOH-AC followed the pseudo-first order model whereas that on DKOH-AC obeyed the pseudo-second order model. The adsorption process was controlled by the intraparticle diffusion combined with the film diffusion model. [ABSTRACT FROM AUTHOR]

The synthesis of metal-organic frameworks (MOFs) with in-built porphyrin units remains challenging. It takes long synthesis time under carefully controlled reaction conditions, and a mixed-phase with different crystal morphologies is still frequently observed. In this work, Zr-based porphyrinic MOF-525 and MOF-545 in high purity and uniform size were produced through a sonochemical route in 2.5 and 0.5 h, respectively, using zirconyl chloride octahydrate and tetrakis (4-carboxyphenyl) porphyrin. Benzoic acid was used as a modulator for MOF-525, and trifluoroacetic acid for MOF-545. The physicochemical properties of the MOF products were examined by X-ray diffraction, scanning electron microscopy, and N 2 adsorption-desorption isotherms. Additionally, the defect sites in the MOF samples were analyzed by UV–vis spectrometry, thermogravimetric analysis, and inductively coupled plasma mass spectrometer. The sonochemically synthesized MOF samples had more defect sites than the conventionally prepared ones and exhibited improved textural properties. In particular, the MOF-545 had a significantly smaller (ca. 1.0 μ m) particle size than the conventionally prepared sample (ca. 4.8 μ m). The MOF-525 and MOF-545 prepared by the sonochemical route exhibited enhanced hydrolysis of the chemical warfare simulant dimethyl-4-nitrophenyl phosphate (DMNP) and a faster and higher bisphenol-A adsorption than the conventionally prepared MOF samples. MOF-525 and MOF-545 were synthesized through a sonochemical route and tested for the hydrolysis of DMNP and adsorption of BPA. Image 1 • Sonochemical syntheses of zirconium-based porphyrinic MOF 525 and 545 were reported. • High-purity crystals of MOF-525 and MOF-545 were obtained within 2.5 h and 0.5 h, respectively. • These MOFs were tested for the hydrolysis of dimethyl-4-nitrophenyl phosphate (DMNP) and adsorption of bisphenol-A (BPA). • Enhanced performances of these MOFs due to increased defect sites, smaller particles size, and larger BET surface area. [ABSTRACT FROM AUTHOR]

High performance adsorption of Gd3+ by the second generation poly(amidoamine) dendrimer immobilized on mesoporous silica foam (MSF) and fibrous nano-silica KCC-1. • Poly(amidoamine) dendrimer was grafted on mesoporous silica foam and fibrous silica KCC-1. • The prepared adsorbents were extensively characterized after each preparation step. • Gd3+ adsorption over the adsorbents was examined under various experimental conditions. • Mesoporous silica foam was more effective as a host than KCC-1 for the dendrimer. • High adsorption capacity and recyclability with good selectivity were confirmed. Separation and recovery of low concentration rare earth elements (REEs) from aqueous environment need to be considered to meet their growing demand for high-technology devices. In this work, the second-generation poly(amidoamine) dendrimers immobilized on a mesoporous silica foam (MSF) or a fibrous nano-silica KCC-1 (PAMAM@GTA-NH 2 -MSF and PAMAM@GTA-NH 2 -KCC-1, respectively) were prepared after systematic grafting of 3-aminopropyltriethoxysilane and glutaraldehyde (GTA) as a cross-linking spacer. These were investigated for recovery of gadolinium ions (Gd3+) in water via adsorption. The prepared adsorbents were extensively characterized in each preparation step by various analytical instruments, and successful attachment of the organic groups on the silica supports was confirmed. The Gd3+ adsorption over the functionalized materials was examined under different conditions of the solution pH, initial Gd3+ concentrations, and adsorption time. PAMAM@GTA-NH 2 -MSF performed better than PAMAM@GTA-NH 2 -KCC-1, with exceptionally high adsorption capacity (ca. 132 mg/g) and recyclability with reasonable selectivity for potential commercial use. Gd3+ selectivity against competing ions could be further enhanced to ca. 86% by successive functionalization with N-(phosphonomethyl) iminodiacetic acid on PAMAM@GTA-NH 2 -MSF. [ABSTRACT FROM AUTHOR]