Evaluation of acid mine drainage sludge as soil substitute for the reclamation of mine solid wastes.

The reclamation of mine waste deposits is often hindered by the scarcity of natural topsoil. Acid mine drainage sludge (AMDS), as a mass-produced waste in metalliferous mines, is a potential topsoil substitute but had not been validated. In this study, a pot experiment with three plant species was conducted to evaluate the capacity of AMDS to support plant growth, buffer acidification, and immobilize heavy metal(loid)s when reclaiming mine waste rocks. Chemical fertilizer and compost chicken manure were applied to AMDS at different rates to explore their effects on plant growth and the physicochemical properties of AMDS. Results showed that all the plants could survive in AMDS even without fertilization. The contents of heavy metal(loid)s in rhizosphere remained almost unchanged over the experimental period, indicating low leachability of revegetated AMDS. Fertilizers enhanced macronutrients and soil enzyme activities, leading to significant increases in plant biomass. However, owing to manure composting and low richness and diversity of the bacterial community in AMDS, the NH4+-N and bioavailable phosphorus contents were extremely low. Bermuda grass was a suitable pioneer species for reclamation for its better adaptability to nutrient deficiency and heavy metal(loid) stress. Overall, AMDS is a viable soil substitute for mine reclamation due to its capability to support plant growth and environmental safety.

Rational Design and Synthesis of a Deep-Ultraviolet Nonlinear Optical Fluorinated Orthophosphate: BaZn(PO4)F.

Rational design and tailored synthesis of noncentrosymmetric compounds with nonlinear optical (NLO) properties, especially in the deep-ultraviolet (deep-UV) region, remains a great challenge. Herein, we report on the development of a modified fluoro-solvo-hydrothermal method with two additive reagents (trimethylamine and NaF solution) as the solvents, using BaFe(PO4)(OH) ( P212121) as the prototype, for the rational design and tailored synthesis of the first deep-UV fluorinated orthophosphate, BaZn(PO4)F. It crystallizes in the polar space group Pna21 and exhibits transparency down to deep-UV region (<190 nm) with SHG effect at 0.26 × KH2(PO4). Its structure is built from strictly alternating ZnO4F trigonal bipyramids and PO4 tetrahedra, resulting in a four-connected ABW-type zeolite framework. First-principles calculations confirm the deep-UV absorption edge and reveal that ZnO4F plays an essential role in the NLO properties. The synergetic effect of Zn and F atoms leads to its more polar crystal structure, much deeper absorption edge, and better SHG effect than the prototype.

Structural diversities induced by cation sizes in a series of fluorogermanophosphates: A2[GeF2(HPO4)2] (A = Na, K, Rb, NH4, and Cs).

Germanophosphates, in comparison with other metal phosphates, have been less studied but potentially exhibit more diverse structural chemistry with wide applications. Herein we applied a hydro-/solvo-fluorothermal route to make use of both the "tailor effect" of fluoride for the formation of low dimensional anionic clusters and the presence of alkali cations of different sizes to align the anionic clusters to control the overall crystal symmetries of germanophosphates. The synergetic effects of fluoride and alkali cations led to structural changes from chain-like structures to layered structures in a series of five novel fluorogermanophosphates: A2[GeF2(HPO4)2] (A = Na, K, Rb, NH4, and Cs, denoted as Na, K, Rb, NH4, and Cs). Although these fluorogermanophosphates have stoichiometrically equivalent formulas, they feature different anionic clusters, diverse structural dimensionalities, and contrasting crystal symmetries. Chain-like structures were observed for the compounds with the smaller sized alkali ions (Na+, K+, and Rb+), whereas layered structures were found for those containing the larger sized cations ((NH4)+ and Cs+). Specifically, monoclinic space groups were observed for the Na, K, Rb, and NH4 compounds, whereas a tetragonal space group P4/mbm was found for the Cs compound. These compounds provide new insights into the effects of cation sizes on the anionic clusters built from GeO4F2 octahedra and HPO4 tetrahedra as well as their influences on the overall structural symmetries in germanophosphates. Further characterization including IR spectroscopy and thermal analyses for all five compounds is also presented.

Multiple Fluorine-Substituted Phosphate Germanium Fluorides and Their Thermal Stabilities.

Anhydrous compounds are crucially important for many technological applications, such as achieving high performance in lithium/sodium cells, but are often challenging to synthesize under hydrothermal conditions. Herein we report that a modified solvo-/hydro-fluorothermal method with fluoride-rich and water-deficient condition is highly effective for synthesizing anhydrous compounds by the replacement of hydroxyl groups and water molecules with fluorine. Two anhydrous phosphate germanium fluorides, namely, Na3[GeF4(PO4)] and K4[Ge2F9(PO4)], with chainlike structures involving multiple fluorine substitutions, were synthesized using the modified solvo-/hydro-fluorothermal method. The crystal structure of Na3[GeF4(PO4)] is constructed by the common single chains ∞1{[GeF4(PO4)]3-} built from alternating GeO2F4 octahedra and PO4 tetrahedra. For K4[Ge2F9(PO4)], it takes the same single chain in Na3[GeF4(PO4)] as the backbone but has additional flanking GeOF5 octahedra via an O-corner of the PO4 groups, resulting in a dendrite zigzag single chain ∞1{[Ge2F9(PO4)]4-}. The multiple fluorine substitutions in these compounds not only force them to adopt the low-dimensional structures because of the "tailor effect" but also improve their thermal stabilities. The thermal behavior of Na3[GeF4(PO4)] was investigated by an in situ powder X-ray diffraction experiment from room temperature to 700 °C. The modified solvo-/hydro-fluorothermal method is also shown to be effective in producing the most germanium-rich compounds in the germanophosphate system.

Dimensional Reduction From 2D Layer to 1D Band for Germanophosphates Induced by the "Tailor Effect" of Fluoride.

The "tailor effect" of fluoride, exclusively as a terminal rather than a bridge, was applied successfully to design low-dimensional structures in the system of transition metal germanophosphates for the first time. Two series of new compounds with low-dimensional structures are reported herein. K[M(II)Ge(OH)2(H0.5PO4)2] (M = Fe, Co) possess flat layered structures built from single chains of edge-sharing M(II)O6 and GeO6 octahedra interconnected by HPO4 tetrahedra. Their fluorinated derivatives, K4[M(II)Ge2F2(OH)2(PO4)2(HPO4)2]·2H2O (M = Fe, Co), exhibit band structures of two four-membered ring germanium phosphate single chains sandwiched by M(II)O6 octahedra via corner-sharing. Both of these structures contain anionic chains of the condensation of four-membered rings built from alternating GeO4Φ2 (Φ = F, OH) octahedra and PO4 tetrahedra via sharing common GeO4Φ2 (Φ = F, OH) octahedra, the topology of which is the same as that of the mineral kröhnkite [Na2Cu(SO4)2·2H2O]. Note that the switch from the two-dimensional layered structure to the one-dimensional band structure was performed simply by the addition of a small amount of KF·2H2O to the reaction mixture. This structural alteration arises from the incorporation of one terminal F atom to the coordination sphere of Ge, which breaks the linkage between the transition metal and germanium octahedra in the layer to form the band structure.

Structural assembly from phosphate to germanophosphate by applying germanate as a binder.

Structural assembly from phosphate to germanophosphate by applying germanate as a binder has been achieved. Two isotypic porous compounds, K3[M(II)4(HPO4)2][Ge2O(OH)(PO4)4]·xH2O (M(II) = Fe, Cd; x = 2 for Fe and 3 for Cd, denoted as KFeGePO-1 and KCdGePO-1, respectively), contain a known transition-metal phosphate (TMPO) layer, (∞)(2){[M2(HPO4)3]2­}, which is built from chains of trans-edge-sharing MO6 octahedra bridged by MO5 trigonal bipyramids that were further linked and decorated by phosphate tetrahedra. The layers are bound by infinite chains of GeO5(OH) octahedra, resulting in a 3D open-framework structure with 1D 12-ring channels that are occupied by K+ ions and water molecules. The curvature of the TMPO layers and shape of the 12-ring windows can be tuned by the transition metals because of their Jahn­Teller effect.

Lithium manganese(II) diaqua-boro-phosphate monohydrate.

The title compound, LiMn(H(2)O)(2)[BP(2)O(8)]·H(2)O, is built up of an open framework of helical borophosphate ribbons inter-connected by MnO(4)(H(2)O)(2) octa-hedra, forming one-dimensional channels along [001] occupied by Li(+) cations and disordered H(2)O mol-ecules (site occupancy 0.5). The Li cations reside in two partially occupied sites [occupancies = 0.42 (3) and 0.289 (13)] near the helices.