K1.65V1.78W0.22O2(AsO4)2

The title potassium vanadium tungsten bis­(arsenate oxide) was synthesized by a solid-state reaction at 973 K. The crystal structure is isotypic with KVOPO4 and contains a [MVAs2O10]∞ framework built up from single MO6 (M = V+W) octa­hedra sharing corners with single VO6 octa­hedra and AsO4 tetra­hedra. This structure shows the existence of infinite [VAsO8]∞ and [MAsO8]∞ chains running along the a and c directions, respectively. All atoms are located on general positions. The metal position M is statistically occupied by 78% V and 22% W

K2V2O2(AsO4)2

The vanadium oxide arsenate with formula K2V2O2(AsO4)2, dipotassium divanadium(IV) dioxide diarsenate, has been synthesized by solid-state reaction in an evacuated silica ampoule. Its structure is isotypic with K2V2O2(PO4)2. The framework is built up from corner-sharing VO6 octahedra and AsO4 tetrahedra, creating an infinite [VAsO8]∞ chain running along the a- and c-axis directions. The K+ cations are located in hexagonal tunnels, which are delimited by the connection of the [VAsO8]∞ chains

Zeolite Waste Characterization and Use as Low-Cost, Ecofriendly, and Sustainable Material for Malachite Green and Methylene Blue Dyes Removal: Box-Behnken Design, Kinetics, and Thermodynamics

International audienceThis study investigated the potential of 4A zeolite, named4AZW in this work, generated by natural gas dehydration units as solid waste after several treatment cycles, as a low-cost adsorbent to separately remove two cationic dyes, methylene blue (MB) and malachite green (MG), from an aqueous solution within a batch process. The adsorbent material was characterized by N(2)gas adsorption-desorption, X-ray fluorescence spectrometry, X-ray diffraction, FT-IR spectroscopy, and the determination of its cation exchange capacity and point of zero charge. The influence of key operating parameters, such as the pH, adsorbent dosage, ionic strength, contact time, initial dye concentration, and temperature, was investigated. Three independent variables acting on MB adsorption performance were selected from the Box-Behnken design (BBD) and for process modeling and optimization. An analysis of variance (ANOVA), an F-test, and p-values were used to analyze the main and interaction effects. The experimental data were satisfyingly fitted with quadratic regression with adjusted R-2= 0.9961. The pseudo-second-order kinetic model described the adsorption of the dyes on 4AZW. The equilibrium data were well-fitted by the Langmuir model for each adsorption system (MB-4AZW and MG-4AZW) with maximum adsorption capacity (q(max)) values of 9.95 and 45.64 mg/g, respectively, at 25 degrees C. Thermodynamics studies showed that both adsorption systems are spontaneous and endothermic