Movement of boron from ulexite and colemanite minerals in sapwood and heartwood of Cryptomeria japonica

This study evaluated boron diff usion from raw boron minerals ulexite and colemanite with low water solubility in comparison to disodium octaborate tetrahydrate(DOT).Tests were conducted using sugi(Cryptomeria japonica(L.)f.D.Don)sapwood and heartwood blocks conditioned to 30,60,and 90%target moisture content.The blocks were fi lled with the boron compounds through treatment holes and diff usion was observed at three assay zones across the blocks after 7,30,60 or 90-day incubation period at room temperatures.For comparison,ethylene glycol was also introduced into the holes to elevate boron diff usion.As expected,diff usion increased with increased moisture content and levels were higher at the 60%and 90%moisture levels compared to the 30%level.With some exceptions,boron levels did not follow consistent gradients with distance away from the treatment hole.Incorporation of ethylene glycol helped increase boron levels,even in heartwood blocks.Boron levels were higher from the ulexite source than from colemanite;however,DOT treatments resulted in the highest boron diff usion rates as a result of greater water solubility compared to both raw boron minerals.The results suggest that ulexite together with ethylene glycol may be useful in both sapwood and heartwood materials when kept at high moisture levels for extended periods.

Comparative evaluation of boron distribution from ulexite,colemanite and DOT rods in Scots pine wood

This study evaluated boron diff usion from rods made of raw boron minerals,ulexite and colemanite with low water solubility,in comparison with di-sodium octaborate tetrahydrate(DOT).Scots pine(Pinus sylvestris L.)sapwood and heartwood blocks were conditioned to target moisture contents of 30%,60%,and 90%.The rods were inserted into the blocks through treatment holes and boron diff usion was observed at three assay zones across the blocks after 7,30,60 and 90-day-incubation at room temperature.Ethylene glycol was also inserted into the holes to improve boron diff usion.Boron levels increased with increased wood moisture content.With some exceptions,boron in the assay zones did not tend to follow consistent amount gradients with distance from the treatment hole.Boron levels from ulexite rods were higher than those from colemanite rods,with DOT rods with the highest diff usion rates as a result of higher water solubility of DOT than ulexite and colemanite.The results suggest that ulexite-based rods may be useful inthe presence of ethylene glycol in sapwood when wood is at high moisture content for extended periods.

Dissolution Kinetics of Calcined Ulexite in Ammonium Chloride Solutions at High Solid-to-Liquid Ratios

The dissolution kinetics of calcined ulexite in ammonium chloride solutions at high solid-to-liquid ratios were investigated. In the experiments, calcination temperature, solution concentration, reaction temperature, and pre-hydration were chosen as parameters. It was observed that the dissolution rate increased with increasing calcination temperature, solution concentration, and reaction temperature, whereas it was not affected by pre-hydration. Employing graphical and statistic methods, the dissolution rate, based on homogeneous reaction model, can be given as: (1-X(B2O3))-1-1= k(c(NH4Cl))1.982t. The activation energy for the dissolution of the ulexite sample calcined at 160 ℃ was found to be 84.04 kJ·mol-1.

A PRELIMINARY INVESTIGATION ON ULEXITE OBTAINED FROM NATURAL BRINE

Ulexite （NaCaB5O9·8H2O） is a common borate in nature. It is mainly distributed in the salt lakes （salars） of South America and Qinghai-Xizang Plateau in China, as well as the Kramer boron deposit of the Tertiary in the west U. S. A. However, few studies have been made on the origin of ulexite up to now, our success in obtaining the ulexite from the natural brine is still the first time in the world.

Soil boron fertilization:The role of nutrient sources and rootstocks in citrus production

Boron （B） is a key element for citrus production, especially in tropical regions, where the nutrient availability is commonly low in the soil. In addition, information about doses, fertilizer sources, methods of application, and particularly, differential nutrient demand of scion/rootstock combinations are required for efficient fertilization of commercial groves. In a non-irri- gated sweet orange orchard （cv. Natal）, grafted onto Rangpur lime, Swingle citrumelo or Sunki mandarin, we studied the application of two sources of B： boric acid （17% B, soluble in water） and ulexite （12% B, partiaJly soluble in water） at four levels of supply （control without B, and soil application of 2, 4 and 6 kg ha-1 yr-1 of B）. The experiment was carried out for three years （2004-2006）. Boron availability in the soil and concentration in the leaves, as well as the fruit yield and quality of trees were evaluated. Soil B extracted with hot water and total leaf B positively correlated with doses of the nutrient applied to the trees. Levels of B in the soil and in the leaves did not vary with fertilizer sources. Fruit yield of trees grafted onto Rangpur lime and Swingle citrumelo was more responsive to B doses than those grafted onto Sunki mandarin. The maximum fruit yield of trees grafted onto Swingle was obtained with 3.2 kg ha-1 yr-1 of B, and leaf B level of 280 mg kg-1 that point out to a highest demand for B when this combination was compared with other rootstocks. Furthermore, fertilization with B did not affect the quality of fruits, but correlated with B and potassium （K） concentrations in the leaves. These results also support that the current recommendations for levels of B in leaves should be revisited.

Biological performance of particleboard incorporated with boron minerals

We compared resistance to decay, mold fungi, termites and insect larvae of particleboards incorporated with the raw boron minerals ulexite and colemanite to that of particleboards impregnated with the commercial boron preservative zinc borate, or boric acid plus a borax mixture. We also quantified water absorption, thickness swell and boron release of particleboards. Ulexite had the best decay resistance, and colemanite had the best termite resistance. However, ulexite and colemanite were not as effective as zinc borate or the boric acid/borax mixture in preventing mold growth. In general, the boric acid/borax mixture combination was more effective against Anobium larvae than the other treatments. Less boron was released by specimens containing zinc borate and colemanite than by those containing ulexite or the boric acid/borax mixture. In general, water absorption and thickness swell were similar among the different treatments, but both were slightly higher in the ulexite-incorporated specimens. Further mechanical tests will be needed to evaluate the particle- board properties and thereby the compatibility of these boron minerals with various manufacturing processes.