Efficient Removal of Pb(II) from Aqueous Medium Using Chemically Modified Silica Monolith

The adsorptive removal of lead (II) from aqueous medium was carried out by chemically modified silica monolith particles. Porous silica monolith particles were prepared by the sol-gel method and their surface modification was carried out using trimethoxy silyl propyl urea (TSPU) to prepare inorganic–organic hybrid adsorbent. The resultant adsorbent was evaluated for the removal of lead (Pb) from aqueous medium. The effect of pH, adsorbent dose, metal ion concentration and adsorption time was determined. It was found that the optimum conditions for adsorption of lead (Pb) were pH 5, adsorbent dose of 0.4 g/L, Pb(II) ions concentration of 500 mg/L and adsorption time of 1 h. The adsorbent chemically modified SM was characterized by scanning electron microscopy (SEM), BET/BJH and thermo gravimetric analysis (TGA). The percent adsorption of Pb(II) onto chemically modified silica monolith particles was 98%. An isotherm study showed that the adsorption data of Pb(II) onto chemically modified SM was fully fitted with the Freundlich and Langmuir isotherm models. It was found from kinetic study that the adsorption of Pb(II) followed a pseudo second-order model. Moreover, thermodynamic study suggests that the adsorption of Pb(II) is spontaneous and exothermic. The adsorption capacity of chemically modified SM for Pb(II) ions was 792 mg/g which is quite high as compared to the traditional adsorbents. The adsorbent chemically modified SM was regenerated, used again three times for the adsorption of Pb(II) ions and it was found that the adsorption capacity of the regenerated adsorbent was only dropped by 7%. Due to high adsorption capacity chemically modified silica monolith particles could be used as an effective adsorbent for the removal of heavy metals from wastewater.     

Complementary electric-LC resonator antenna for WLAN applications

In this paper, a metamaterial antenna based on complementary electric-LC (CELC) resonator is proposed. The antenna consists of slot-loaded ELC on the ground plane as the main antennas radiating element and excited by a microstrip line. The CELC resonator is characterized by single-negative magnetic moment excited by coupling between the microstrip transmission line and slot-loaded CELC. The peak realized gain and efficiency of 2.63 dB and 86 % are obtained, respectively, at resonance frequency. Simulation and measurement results are presented to validate the design. The antenna is suitable for WLAN applications (2.39–2.48 GHz).     

A new approximation method for common fixed points of families of nonexpansive maps and solution of variational inequalities problems

In this paper we prove a strong convergence of both implicit and explicit shcemes to a common fixed point of finite family of nonexpansive maps which is also a unique solution of some variational inequality problem in Banach space. The result presented here improve and unify several important results recently announced.     

Catalyst and solvent-free, ultrasound promoted rapid protocol for the one-pot synthesis of α-aminophosphonates at room temperature

An ultrasound promoted easy, efficient, and environment friendly process has been devised for the synthesis of α-aminophosphonates within seconds through a one-pot three-component condensation of the aldehydes, amines, and triethylphosphite. The desired products were obtained in excellent yields and in high purity under solvent-free and catalyst-free conditions. Study with various aldehydes and amines reveals that ultrasound radiation plays a key role in the direct synthesis of α-aminophosphonates.     

Variational Approach to Homoclinic Solutions for Fractional Hamiltonian Systems

In this paper, we discuss the existence and multiplicity of homoclinic solutions for fractional Hamiltonian systems with left and right Liouville–Weyl fractional derivatives. Sufficient conditions ensuring the existence of an unbounded sequence of homoclinic solutions for the given problem are obtained via variational approach.     

Sulfated Triterpenes from Lemon Balm

The hydroalcoholic (EtOH/H₂O) extract of matured leaf margins of lemon balm (Melissa officinalis L.) afforded a new 3,23‐disulfate of 2α,3β‐23,29‐tetrahydroxyolean‐12‐en‐28‐oic acid 28‐O‐β‐D ‐glucopyranoside ( 1 ) and a new 23‐monosulfate of 2α,23‐dihydroxyurs‐12‐en‐28‐oic acid 3‐O‐β‐D ‐glucopyranoside ( 2 ), along with six known compounds, i.e., 23‐monosulfate of 2α,3β,19α,23‐tetrahydroxyurs‐12‐ene‐28‐oic acid 28‐O‐β‐D ‐glucopyranoside ( 3 ), 3,5,6‐trihydroxydehydro‐α‐ionol 9‐O‐β‐D ‐glucopyranoside ( 4 ), quadranoside III ( 5 ), rosmarinic acid ( 6 ), caffeic acid ( 7 ), and luteolin ( 8 ). All the isolated compounds were evaluated for their antioxidant, antimicrobial, antimalarial, and cytotoxic activities. Only rosmarinic acid exhibited substantial antioxidant and antimicrobial activities, whereas sulfated terpenes showed considerably lower or no antimicrobial activity.     

Heterogeneous reusable catalyst,ultrasound energy,and no solvent: a quick and green recipe for one-pot synthesis of β-phosphonomalononitriles at room temperature

Clay-supported heteropolyacid catalyst has been prepared and investigated as a novel heterogeneous, reusable and efficient catalyst for the one-pot synthesis of β-phosphonomalononitriles under ultrasound irradiation at room temperature. Compared with traditional methods, the present method is solvent-free, works under milder and cleaner conditions, furnishes products with higher purity and yields, needs shorter reaction time, easier work-up procedure, and generates less waste. No column purification is required and the products can be purified by simple crystallization. The catalyst can be easily recovered and reused several times without significant loss of its catalytic activity. The catalyst was characterized by scanning electron microscopy, X-ray powder diffraction, and thermal gravimetric, surface area, and elemental analyses.