Solid-Liquid Phase Equilibria of the Pb2+, Ca2+, Mg2+//Cl--H2O Quaternary System and Its Subsystems at 303.2 K.

The solid-liquid phase equilibria of the ternary systems Pb2+, Ca2+//Cl--H2O, Pb2+, Mg2+//Cl--H2O, and Ca2+, Mg2+//Cl--H2O were investigated at atmospheric pressure and T = 303.2 K using the isothermal dissolution equilibrium method. Additionally, solid phase equilibria of the quaternary system Pb2+, Mg2+, and Ca2+//Cl--H2O were determined, and the corresponding stable phase diagrams and density-composition diagrams were constructed. The results indicate that the phase diagrams of Pb2+, Ca2+//Cl--H2O mainly consist of a ternary invariant point, two solubility curves, and four crystalline regions, while there are two ternary invariant points, three solubility curves, and six crystalline regions in the Pb2+, Mg2+//Cl--H2O and Ca2+, Mg2+//Cl--H2O systems. The results of the density-versus-w(CaCl2) plots of the various ternary systems confirm that the density of the equilibrium solution tends to go upward with the increase in the mass fraction of CaCl2. The density of various ternary systems reaches the maximum and equilibrium at the corresponding invariant point, and there is no significant change with the further increase in the CaCl2 mass fraction. Furthermore, the phase diagram of the Pb2+, Mg2+, Ca2+//Cl--H2O quaternary system includes two invariant points, five isothermal dissolution curves, and five crystalline regions. The order of the relative areas of the crystalline regions for the five salts is PbCl2 > CaCl2·2MgCl2·12H2O > 2PbCl2·3MgCl2·18H2O > MgCl2·6H2O > CaCl2·4H2O.

Facile preparation of multi-porous biochar from lotus biomass for methyl orange removal: Kinetics, isotherms, and regeneration studies.

Biomass is a promising carbon source because of its low-cost and rich carbon component. Here, lotus root as self N-source was used to produce N-doped biochar via a simple carbonization after freeze-drying, showing surface areas up to 694 m2/g with partial mesopores. Applicability of biochar as adsorbent for dyes removal was explored using methyl orange (MO) as model pollutant dye. LBC-800 sample obtained at 800 °C had the largest capacity of 320 mg/g in 300 mg/L solution at 25 °C with fast equilibrium time of 60 min, and pseudo-second order model expressed better for kinetics. LBC-800 also had an unprecedented maximum capacity of 449 mg/g with superior conformity to Langmuir model. The biochar was efficient for MO removal with high capacity and fast kinetic, and significantly the sustainable feature of lotus root would allow a large-scale production of biochar as well as promising use in wastewater treatment fields.

Fabrication of N-doped carbons from waste bamboo shoot shell with high removal efficiency of organic dyes from water.

N-doped carbons were obtained from bamboo shoot shell via hydrothermal pretreatment under salt assistance followed by carbonization, using melamine as nitrogen source. The carbons with tubular morphology and surface areas in 406-489 m2/g range were used as adsorbents for the removal of methyl orange (MO) and rhodamine B (RhB). Adsorption isotherms and kinetic fitting showed much better accordance with Freundlich model and pseudo-second-order, showing balanced capacity (qe) of 50 mg/g for MO and 42 mg/g for RhB on the pristine carbons (BHC-800) at 25 °C. After N-doping treatment, carbons (BSC-M20) had qe of MO and RhB up to 140 and 100 mg/g, respectively, confirming a positive effect of N-doping on the enhancement of dyes removal. The findings indicated that hydrothermal treatment followed by carbonization was efficient to obtain N-doped carbons from biomass materials, and the present BSS-derived carbons were promising adsorbents for organic dyes removal from water.