A green process to prepare chromic oxide green pigment.

A hydrogen reduction and activated sintering process was proposed to prepare chromic oxide green pigment. Through ICP, XRD, SEM, FT-IR, UV, and CIE-L*a*b* colorimetric analysis, key factors and mechanism that influenced preparation of chromic oxide green pigment were studied. The results revealed that lower hydrogen reduction temperature, suitable addition of Al and Ba, were beneficial to obtaining the high quality chromic oxide green pigment. Typically, when the hydrogen reduction temperature was kept at 450-500 degrees C, physicochemical properties and color performance of the prepared chromic oxide green pigment doped with about 0.1-0.2 wt % Al and 0.2-0.5 wt % Ba conformed to commercial pigment standards. Additionally, characteristics of the green process were discussed. About 90 wt % KOH was reused directly and about 90 wt % Cr(VI) was conversed to Cr(III) directly from potassium chromate to chromic oxide green pigment. Integrating the proprietary green metallurgical process from chromite ore to potassium chromate of this laboratory, more than 99 wt % Cr(VI) could be conversed to Cr(III) compounds and about 99 wt % KOH could be recycled to use. The whole green process, ranging from chromite ore to chromic oxide green pigment, eventually not only provided the possibility for producing the high quality chromic oxide green pigment, but could reach comprehensive utilization of resources, inner recycle of KOH, and zero emission of Cr(VI).

[Synthesis, characterization and study on vibration spectra of potassium triborate].

Potassium triborate was synthesized with potassium carbonate and boric acid by controlling suitable feed mixture ratio, reaction temperature and dehydration temperature in the self-designed boiling reactor. According to chemical analysis, the formula of the synthetics was monohydrate potassium triborate (KB3O5 x H2O). It's structure was characterized by XRD, FTIR, Raman and TG, and it was found by XRD analysis that the synthetics was amorphous solid. FTIR and Raman spectroscopy anal-ysis show that three coordination B(3) -O bond, four coordination B(4) -O bond, and hydroxy and triborate anions existed in the formula of the synthetics. Thermogravimetric (TG) analysis show that the groups which can lose mono-water existed in the formula of the synthetics, and structural formula of the synthetics was deduced as K[B3O4 (OH)2]. Vibration spectra of the synthetics were studied, including FTIR and Raman spectroscopy. Vibration absorption peaks of some main groups of the synthetics were investigated, including three coordination B(3) -O bond and four coordination B(4) -O bond that are the main existing forms of boron atoms in the synthetics as well as other groups, and each vibration absorption peak was assigned.

[Analysis of trace elements in corncob by microwave digestion-ICP-AES].

The contents of trace elements of Zn, Mg, Mn, Sr, Fe, Pb, Cu and Se in the corncob collected from Beijing, Shan-dong, Jilin, Yunnan, Xinjiang, Gansu, Shanxi, Shaanxi, Jiangsu, Neimeng in China were determined by ICP-AES using microwave digestion. The optimum condition of digesting the corncob was: put 1.5 mL of 68% nitric acid and 0.5 mL of hydrofluoric acid in the pot, then digested the sample with 3 steps under the 400 W power in the microwave oven. This digesting procedure could completely and quickly digest the sample. The relative standard deviations and recovery yield are 0.72%-4.16% and 95.5%-104.5% for Zn, 1.58-3.66% and 98.2%-103.5% for Mg, 0.19%-4.58% and 97.0%-103.2% for Mn, 1.31%-4.90% and 95.7%-104.1% for Sr, 1.40%-4.01% and 95.9%-104.6% for Fe, 1.55%-4.28% and 95.1%-104.5% for Pb, 2.16%-5.00% and 96.4%-103.5% for Cu, and 2.00%-4.99% and 95.1%-101.3% for Se, respectively. The analysis of the trace metals by the method of ICP-AES using the method of microwave digestion proved to be easily operational, rapid, highly sensitive, and accurate. It could be adopted as the method of determining many elements simultaneously.

[Application of FTIR and XPS technique to the analysis of the mixture containing chromium in a low valence state].

Chromium has various valence states and in the process of preparing chromium oxides with low valence state of chromium, chromium compounds with different valence state of chromium can usually be produced as intermediates. Due to the difference in property of these intermediates, they always have remarkable influences on the morphological characteristics of the final product. The composition of the intermediate was very complicated in the process of synthesizing chromium oxide with low valence state of chromium by reducing potassium chromate with hydrogen. To explore the reaction mechanism and further optimize the technical process, the composition of the intermediate obtained from the reduction of K2CrO4 with hydrogen was investigated through the combination of XPS, FTIR and XRD. The XPS results revealed that the intermediate of reducing potassium chromate with hydrogen is trivalent chromium compound; the results of FTIR and XRD indicated that the intermediate mainly consists of Cr(OH)3 x nH2O, HCrO2 and a little amount of KOH or KCrO2. On the basis of the above analysis of the intermediate, the possible reactions that occurred in the reduction process were suggested.

[Analysis of trace elements in corn stover by ICP-AES].

The contents of trace elements of Zn, Mg, Mn, Sr, Fe, Co, Ni and Se in the corn stover collected from Shanxi, Beijing, Xinjiang, Shandong, Neimeng, Gansu, Shaanxi, Jilin, Yunnan and Jiangsu, 10 different provinces in China, were determined by ICP-AES using nitrifying method of high pressure nitrifying pot. This method proved to be easily operational, rapid, highly sensitive, and accurate, and can be adopted as the method of determining many elements simultaneously. The recovery yields of Zn, Mg, Mn, Sr, Fe, Co, Ni and Se are 96.55%-103.8%, 98.0%-102.5%, 95.7%-104.1%, 97.1%-103.2%, 95.1%-101.3%, 95.1%-104.5%, 97.0%-103.5% and 95.9%-104.6%, respectively, and the relative standard deviation of all the elements is all below 5.00%.

[Study on the corn stover lignin oxidized by chlorine dioxide and modified by furfuryl alcohol].

The Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Visible), nuclear magnetic resonance spectroscopy (1H NMR) and TG analysis were used to study the oxidation of corn stover lignin by chloride dioxide and subsequently modified by furfuryl alcohol. The results were as following: The selective oxidation of lignin by chlorine dioxide was obtained by spectroscopy study. FTIR showed that the characteristic absorbance peaks of aromatic units were decreased after chloride dioxide oxidation. The increased absorbance for the band around 1720 cm(-1) corresponding to carbonyl stretching was achieved in the oxidized lignin and the lignin modified with furfuryl alcohol. The ultraviolet-visible spectroscopy showed that the absorbance around 280 nm was largely reduced after the lignin was oxidized. The 1H NMR spectroscopy also showed the decrease of aromatic units and methoxyl group in the oxidized lignin. All these indicated the formation of muconic acid and ester, or quinone derivatives when the lignin was selectively oxidized by chloride dioxide. The modification by furfuryl alcohol made the oxidized lignin more thermally stable.

[Study on vibration spectrum and properties of anhydrous potassium pentaborate crystal at high temperature].

The effect of water vapor on the structure of anhydrous potassium pentaborate was studied at high temperature by self-designed reactor in the present paper. The vibration spectra of anhydrous potassium pentaborate crystal at high temperature were analyzed by X-ray diffraction spectrum(XRD), infrared spectrum (IR) and Raman spectrum. The ratio of B2O3 to K2O in potassium pentaborate was diminished by reacting with water vapor. XRD analysis shows that K5B19O31 exists inpotassium pentaborate crystal at 750 degrees C, while IR and Raman analysis show that some triangular structure units(B(3)--O) are changed to tetrahedral structure units(B(4)-O) in the crystal. The content of tetrahedral structure unit(Br(4) -O) increases and the network configuration between boron and oxygen is farther broken.

Studies on thermal dehydration of hydrated chromic oxide.

Hydrated chromic oxide was prepared by the reduction of potassium dichromate in an autoclave using sucrose. The thermal dehydration of the parent gel in different atmospheres was studied comparatively using the techniques of thermal gravimetry, differential thermal analysis, X-ray diffraction analysis, FT-IR spectroscopy, and gas adsorption. The results of thermogravimetric and differential thermal analysis show that the temperature at which the glow phenomenon occurs is dependent on the gaseous atmosphere in the heat-treatment process and increases in the following order: air, nitrogen, and carbon dioxide. When heated in CO(2), the parent gel is transformed into crystalline alpha-Cr(2)O(3) going through the phase of amorphous Cr(2)O(3). In air, however, it is decomposed directly into crystalline alpha-Cr(2)O(3) without going through the amorphous Cr(2)O(3) phase. It is also found that microcrystallites of alpha-Cr(2)O(3) have been formed before the glow phenomenon occurs at 390 degrees C in air and at 590 degrees C in CO(2), respectively. The mechanism for thermal dehydration in air and CO(2) is discussed.