Intensifying gibbsite precipitation from sodium aluminate solution by adding a mixed seed

Gibbsite precipitation from sodium aluminate solution was intensified by adding mixed industrial and self-prepared active seeds,and its mechanism was researched preliminarily.The interfacial properties of seed/aluminate solution were determined for separate industrial and active seed.Contact angles of seed/aluminate solution and the specific surface area of seeds were respectively measured by sessile drop and BET method,and the morphology and particle size of precipitates were recorded by SEM and laser diffraction.The results show that,compared with the industrial seed,the active seed has a better wettability,lower interfacial tension,and larger specific surface area,being conducive to enhancing gibbsite precipitation from sodium aluminate solution.SEM analysis of the precipitates indicates that the embedment and accumulation/agglomeration of extremely fine particles on the surface of coarse industrial seed can effectively control the content of fine particles in the precipitation product.With extra 3.1–4.6 g/L active seed,the gibbsite precipitation ratio was increased by 3.23%–3.92%.Moreover,the mass percentage of particles<45μm in precipitation product has even a slight decrease compared with that for the traditional precipitation product or of the industrial seed itself.The result presented is favorable to developing an intensified gibbsite precipitation process for commercial alumina manufacture.

Seed Priming with Beta-Amino Butyric Acid Improves Abiotic Stress Tolerance in Rice Seedlings

We studied the influence of seed priming with beta-amino butyric acid（BABA） on the growth, physiological and biochemical parameters of seedlings with varied abiotic stress tolerance, which were raised and grown under unstressed and stressed（NaCl/PEG-6000） conditions. Under stressed conditions, the growth of rice seedlings was less when compared to control plants. After BABA priming, the seedling growth increased both under unstressed and stressed conditions as compared to the respective controls. BABA priming of rice seeds caused increase in the photosynthetic pigment content of the leaves, modified the chlorophyll a fluorescence related parameters and also enhanced the photosystem activities of seedlings when compared to their respective non-primed controls. BABA priming also caused increased mitochondrial activities of the rice seedlings. Moreover, BABA priming significantly reduced malondialdehyde content in the seedlings and also resulted in accumulation of proline especially in the NaCl tolerant variety Vyttila 6. BABA seed priming also enhanced the activity of nitrate reductase enzyme and activities of antioxidant enzymes like guaiacol peroxidase and superoxide dismutase. The presence of BABA was detected by high performance thin layer chromatography analysis in the rice seeds whereas in the seedlings it was not detected. Thus, it can be inferred that the seed priming effect of BABA mainly occurred within the seeds, which was further carried to the seedlings. It is concluded that BABA priming of seeds improved the drought and salinity stress tolerance of all the three rice varieties and it was significantly evident in the drought tolerant variety Vaisakh and NaCl tolerant variety Vyttila 6, when compared to the stress sensitive variety Neeraja.

Study on Damage Characteristics of Weedy Rice

In this study, several typical tralts of weedy rice and its damage charac-teristics were analyzed. The resuIts showed that the shattering of weedy rice was sometimes weaker than that of conventional rice. The newIy-harvested weedy rice seeds have certaln dormant period and a Iong active period, whiIe the conventional rice seeds have no dormant period but have a Iimited active period. In the direct seeding and intercropping rice fields where weedy rice occurs seriousIy Iast year, if not controI ed timeIy, weedy rice may caused a damage above 28%, sometimes even above 99%. After one season of cuItivation, the underground weedy rice and conventional rice seeds wiI be carbonized, Iosing their activity. The germination of underground weedy rice can be first induced, and when the Iast-season wheat is harvested, the germinated weedy rice can be kiI ed with 41% gIyphosate （3 000 mI/hm2）, thus the damage and expansion of weedy rice wiI be effectiveIy controI ed.