Study on strength characteristics and thickening characteristics of classified-fine cemented backfill in gold mine.

For some new mines, the utilization rate of tailings is not satisfactory when using unclassified tailings as backfill aggregate for cemented backfill. At the same time, with the progress of mineral processing technology, the tailings discharged by the concentrator gradually become finer. Therefore, cemented filling with fine-grained tailings as aggregate will become the development direction of filling technology in the future. In this paper, the feasibility of fine particle tailings backfill is studied by taking the particle tailings of-200 mesh as aggregate in Shaling gold mine. The calculation shows that the utilization rate of tailings is increased from 45.1% to 90.3% by using-200 mesh tailings as filling aggregate. The response surface central composite design method (RSM-CCD) was used to study the strength of backfill with alkali-activated cementitious material as binder by taking the mass concentration of backfill slurry and sand-binder ratio as input factors. The results show that the 28-day strength of the backfill with graded fine-grained tailings as filling aggregate can reach 5.41 MPa when the sand-binder ratio is 4, which can fully meet the needs of the mine for the strength of the backfill. The thickening test of-200 mesh fine particle tailings was carried out by static limit concentration test and dynamic thickening test. In the case of adding 35 g/t BASF 6920 non-ionic flocculant, the concentration of 64.74% tail mortar can reach 67.71% after 2 h of static thickening, and the concentration can reach 69.62% after 2 h of static thickening. The feeding speed of thickener should be controlled between 0.4 and 0.59 t/(m2 h). In this case, the underflow concentration of thickener is relatively high, which is 64.92-65.78%, and the solid content of overflow water is less than 164 ppm. The conventional full tailings thickening process was improved by using the design of high-efficiency deep cone thickener and vertical sand silo. The feasibility of fine-grained tailings as filling aggregate was demonstrated by combining the filling ratio test of fine-grained tailings, the data of thickening test and the improved thickening process. The research results can provide reference for other mines to use fine-grained tailings as filling aggregate to design filling system.

Synthesis, crystal structure and fluorescence of an unusual terbium carboxylate.

A novel terbium-containing fluorescent material, [Tb(CH3COO)2(H2O)3]Cl (1), has been prepared by a facile approach, i.e. an ultrasonic synthesis. Compound 1 has been structurally characterized via single-crystal X-ray diffraction and it crystallizes in the space group P21/n of the monoclinic system with four formula units in a cell. Compound 1 features a novel one-dimensional (1-D) chain-like structure. The 1-D chains are interconnected by hydrogen bonds to yield a 3-D supramolecular framework. Photoluminescent investigation reveals that compound 1 displays strong emission bands identified as the characteristic emissions of 5D4 → 7FJ (J = 3, 4, 5, 6) of Tb3+.

(µ-4,4'-Bipyridine-κN:N')bis-[triaqua-(4,4'-bipyridine-κN)(3-nitro-phthalato-κO)cobalt(II)].

The title binuclear complex, [Co(2)(C(8)H(3)NO(6))(2)(C(10)H(8)N(2))(3)(H(2)O)(6)], has been synthesized hydro-thermally from 3-nitro-phthalic acid (H(2)NPA), Co(NO(3))(2)·6H(2)O and 4,4'-bipyridine (4,4'-bipy). The mol-ecule of the complex occupies a special position on an inversion centre. The Co(II) atom has a slightly distorted octa-hedral environment formed by two N atoms from two 4,4'-bipy ligands, one carboxyl-ate O atom from NPA, and three O atoms of water mol-ecules. An extensive O-H⋯O and N-H⋯O hydrogen-bonding system links mol-ecules of the complex into a three-dimensional network.

Na(6)(H(2)O)(20)(V(10)O(28)) x 4H(2)O, a novel polyvanadate(V) with a three-dimensional framework.

The novel title polyvanadate(V), poly[[octa-mu-aqua-dodecaaqua-mu(4)-octacosaoxidodecavanadato-hexasodium] tetrahydrate], [Na(6)(H(2)O)(20)(V(10)O(28)).4H(2)O](n), contains [V(10)O(28)](6-) anions which lie about inversion centres and have approximate 2/m symmetry and which are linked to [Na(3)(H(2)O)(10)](3+) cations through two terminal and two mu(2)-bridging O atoms. The structure contains three inequivalent Na(+) cations, two of which form [Na(2)(H(2)O)(8)](n) chains, which are linked via NaO(6) octahedra involving the third Na(+) ion, thus forming a three-dimensional framework.