INVESTIGATION OF THE PROCESS OF PROCESSING LIQUID WASTE OF UREA PRODUCTION USING A BIOFILTER

The kinetic regularities of the recycling process of liquid waste of urea on the combined filter which contains the immobilized layer of enzymes at the process of their purification from the suspended substances, dissolved nitrate anions; the effect of pH on the filtration process are investigated and established in our research. A stable positive result was obtained on the filters with layers of: – oak and birch, the concentration of nitrate anions decreased from 12 to 0,06 — 0,05 mg/dm3 after 80 minutes of filtration. The content of suspended solids decreased from 37 g/dm3 to 6 — 7 g/dm3. At the same time, the increased content of tannins and the natural structure of oak and birch leaves contributes to the resistance of the leaf layer to fermentation processes, helps to use such kind of filter repeatedly. – linden and maple leaves, the concentration of nitrate anions decreased from 12 mg/dm3 to 0,08 mg/dm3 after 80 minutes of filtration. The content of suspended solids decreased from 37 g/dm3 to 15 g/dm3 after the third use of the filter, due to increased activity of microorganisms. At the same time, the natural structure of linden and maple leaves is thin, has a biofilm that is easily destroyed and accelerates the process of natural aerobic fermentation. The scientific substantiation of the direction of improvement of technology of processing of liquid waste with the increased content of nitrogen is executed. A bio filtration unit on a combined filter with a layer of oak and birch leaves with the use of an immobilized layer of enzymes is proposed. The combined filter consists of a layer of gravel, sand and dry oak and/or birch leaves. The enzyme Chymotrypsin at a concentration of 0,005 g/dm3 is fed into the formed bio filter from above. After 30 minutes, liquid waste with a temperature of 10 25 °С is gradually fed into the filter over 60 — 80 minutes. The initial concentration of suspended particles in liquid waste should not exceed a concentration of 37 — 40 g/dm3. It is determined that the optimal rate of processing of liquid waste of urea production is achieved in solutions with active reaction of hydrogen ions in the range of 6,5—7,3.

Synthesis, crystal structure and Hirshfeld surface analysis of copper(I) nitrate -complex based on 1-(2,6-dimethylphenyl)-5-allylsulfanyl-1H-tetrazole

By means of the alternating current electrochemical technique and starting from copper wire electrodes in propanol solution of corresponding ligand and copper(II) nitrate, novel copper(I) -complex [Cu2(C12H14SN4)2(NO3)2] (1) has been obtained and X-ray structurally investigated: sp. gr. , a=7.352(3) Å, b=8.269(3) Å, c=12.723(4) Å, =82.08(3)0, =82.74(3)0, =88.37(3)0, V=759.9(5) Å3, Z=2, dcalc=1.625 g cm–3, (CuK)=3.502 mm–1, max=67.960, 4119 measured reflections, 1248 used reflections, 201 refined parameters, R(F2)=0.0915, S=0.95. The trigonal-pyramidal copper(I) coordination environment consists of nitrogen atom and allylic group of ligand, and of two oxygen atoms from crystallographically distinct nitrate anions. Due to a bridging function of oxygen atoms of nitrate anions, two metal-containing polyhedra are connected into {Cu2L2(NO3)2} topological units which are additionally stabilized by noncovalent interaction CuO(2). Comparatively weak hydrogen bonds C–HO exist in the crystal structure of [Cu2(C12H14SN4)2(NO3)2] (1).

Removal of Nitrate Ions Using Thermally and Chemically Modified Bioadsorbents

Nitrate ions are one of the causes of surface water eutrophication. In the present research, the effective adsorption of nitrate ions (NO3) on bioadsorbents prepared from yam skins (Dioscorea alata) was evaluated. The yam skin was chemically modified with ammonium chloride (NH4Cl), and biochar was prepared from the thermally modified biomass. The results were compared with commercial coal (CC). The bioadsorbents were characterized by SEM-EDS analysis, which showed that the synthesized adsorbents have a heterogeneous surface with pores. The batch adsorption tests showed that the pH has the most significant effect on the NO3 adsorption capacity when using the modified yam skin (MYP), obtaining as best conditions pH 12 and a 0.5 mm particle size with an adsorption capacity of 25.75 mg/g; the best adsorption capacity when using the carbon synthesized from yam skin (CYP) and CC was obtained at pH 2, reaching values of 36 and 33.34 mg/g, respectively. The following performance in terms of adsorption capacity was found: CYP > CC > MYP, according to Langmuir’s model. The equilibrium isotherm of NO3 adsorption on MYP and CYP was adjusted by the Freundlich model, while the Langmuir model described adsorption on CC. The kinetics of all the systems studied showed a good fit to the pseudo-first-order, pseudo-second-order and Elovich models with R2 > 0.95, suggesting a mechanism of chemical adsorption by means of species exchange between the aqueous phase and the surface of the material, with the intervention of an intraparticle diffusion stage; based on these findings, the studied biomasses reached promising adsorption capacities in the removal of nitrate anions, showing that the carbon synthesized from yam skins and modified with ammonium chloride had a remarkable behavior in comparison with commercial carbon and NH4Cl-modified yam skins.

Synthesis, Characterization and Single Crystal X–ray Crystallography of Nd(III) and Pr(III) Complexes with the Tridentate Schiff Base Ligand N'–(1–(pyridin–2–yl)ethylidene)nicotinohydrazide

The use of N'–(1–(pyridin–2–yl)ethylidene)nicotinohydrazide (HL) in lanthanide(III) chemistry has yielded one mononuclear and one dinuclear complexes. The 1:1 Nd(NO3)3.6H2O or Pr(CH3COO)3.6H2O/HL in methanol afforded the complexes [Nd (HL)2(NO3)2(H2O)2].(NO3) (1) and {[Pr(L)(h2–OOCCH3)(H2O)](h1:h2:m–OOCCH3)2[Pr (L)(h2–OOCCH3)(H2O)]} (2). The structures of the complexes were solved by single crystal X–ray crystallography. In the mononuclear complex, the Nd3+ atom is coordinated by two neutral molecules of ligand acting in tridentate fashion, two nitrate anions acting in bidentate manner and two coordinated water molecules yielding a twelve–coordinated Nd atom. In the complex (2) the Pr3+ atoms are doubly bridged by two acetates anions and each metal ion is coordinated by one tridentate monodeprotonated molecule ligand, one bidentate acetate group and one coordinated water molecule. Each Pr3+ atom is nine–coordinated with an environment best described as a tricapped prismatic geometry. Complex 1 crystallizes in the monoclinic space group C2/c with the following parameters: a = 22.7657(8) Å, b = 8.4276(3) Å, c = 18.0831(7) Å, b = 114.851(2)°, V = 3148.2(2) Å3, Z = 4, R1 = 0.032, wR2 = 0.098. Complex 2 crystallizes in the monoclinic space group P21/n with the following parameters: a = 11.5388(6) Å, b = 14.1087(8) Å, c = 12.2833(6) Å, b = 102.211(2)°, V = 1954.45(18) Å3, Z = 2, R1 = 0.029, wR2 = 0.066. The supramolecular structures are consolidated by multiple hydrogen bonds.

Investigating the Potential of Flexible and Pre-Organized Tetraamide Ligands to Encapsulate Anions in One-Dimensional Coordination Polymers: Synthesis, Spectroscopic Studies and Crystal Structures

The synthesis of amide-based molecules, possessing pre-organized structures, has received significant attention due to their potential applications as molecular receptors and as components of nanomaterials. In this study, four extended tetraamide ligands incorporating ethylene and propylene spacers, namely 1,2-bis[N,N′-6-(3-pyridylmethylamido)pyridyl-2-carboxyamido]ethane (L1), 1,2-bis[N,N′-6-(4-pyridylmethylamido)pyridyl-2-carboxyamido]ethane (L2), 1,2-bis[N,N′-6-(3-pyridylmethylamido)pyridyl-2-carboxyamido]propane (L3) and 1,2-bis[N,N′-6-(4-pyridylmethylamido)pyridyl-2-carboxyamido]propane (L4), were successfully synthesized. Further, reaction of L2 and L4, incorporating pendant 4-pyridyl donors as the metal coordinating sites, with cadmium salts, produced two close-packed one-dimensional coordination polymers, {[Cd3(L2)4(H2O)10](NO3)6·12H2O·CH3OH}n and {[Cd(SO4)(L4)(H2O)2]·4H2O·CH3OH}n. X-ray crystallography reveals that the flexible tetraamide ligands fold upon themselves in the coordination polymer structure. As a consequence, the anion pocket in {[Cd(SO4)(L4)(H2O)2]·4H2O·CH3OH}n incorporating the ligand with the propylene spacer was blocked from encapsulating charge-balancing anions, which were involved in bridging the di-cadmium units. Interestingly, a strong interaction between the 2,6-pyridine dicarboxamide moiety with the nitrate anions was found in {[Cd3(L2)4(H2O)10](NO3)6·12H2O·CH3OH}n, showing potential for materials made from these ligands to serve as anion receptors.

Efficient Exfoliation of Layered Double Hydroxides; Effect of Cationic Ratio, Hydration State, Anions and Their Orientations

The exfoliation ability of nitrate based Mg1−xAlx(OH)2(NO3)x·mH2O layered double hydroxides (Mg-Al LDH) in formamide into single or multilayer nanosheets depends strongly on nitrate anion orientation and layer charge. Our systematic studies used materials that were likely to disclose differences with respect to anion type and their concentrations in the interlayer gallery. We assured to avoid any carbonate incorporation into the galleries for nitrate, chloride, iodide, and sulfate based Mg-Al LDHs. Furthermore, the comparative exfoliation experiments were conducted for fully hydrated samples with as similar particle morphology as possible. The exfoliation of nitrate Mg-Al LDH is far superior to similar clays with carbonate, sulfate, chloride, or iodide as charge balancing anions. Quantitative analysis of exfoliation yield for pre-treated, fully hydrated samples, shows an optimum composition for exfoliation into single nanosheets of around x ≈ 0.25, while double or triple layered sheets are encountered for other x-values. We observe a clear correlation between the expansion of the interlayer gallery due to progressing tilts of nitrate anions and water molecules out of the horizontal interlayer plane, suspension turbidity, and degree of exfoliation. The established correlations extends to nitrate Ni-Al LDH materials. We finally claim that morphology is a dominating parameter, with house-of-card morphology particles exfoliation far less than platelet-like particles. Hence, hydrothermal treatment may be favorable to enhance exfoliation yields.

Structure and surface properties of Ni-Al hydrotalcite-like compounds and their catalytic application in highly selective acetalization at room temperature

The Ni-Al hydrotalcite-like compounds (Ni-Al HTLCs) containing nitrate anions were synthesized and applied in the acetalization of p-anisaldehyde with ethylene glycol under mild reaction conditions. The Ni-Al HTLCs showed good...

A proton-responsive ligand becomes a dimetal linker for multisubstrate assembly via nitrate deoxygenation

A bidentate pyrazolylpyridine ligand (HL) was installed on divalent nickel to give [(HL)2Ni(NO3)]NO3. This species is reacted with TMS2Pz to simultaneously reduce one of the nitrate anions and deprotonate one of the ligands.

Design of Anion–π Interactions and Hydrogen Bonds to Recognition of the Chloride, Bromide and Nitrate Anions

The role of anions in several biochemical processes gives rise to an enormous interest in the identification/exploration of compounds with potential ability to recognize anions. Here, the anthracene–squaramide conjugated compounds,...