China
Africa
Explore chapters and articles related to this topic
B, 5]
Published in Alina Kabata-Pendias, Barbara Szteke, Trace Elements in Abiotic and Biotic Environments, 2015
Alina Kabata-Pendias, Barbara Szteke
Boron is widely distributed in the hydrosphere, and its water solubility highly controls its distribution in the environment. The largest quantities of B are accumulated in marine evaporites and marine argillaceos sediments. Borate minerals are usually deposited as evaporates (e.g., borax and kernite). Boron may also be increased in some volcanic emissions, mainly as orthoboric acid, H3BO3, and thus it occurs in higher amounts in volcanic rocks.
Industrial minerals
Published in Francis P. Gudyanga, Minerals in Africa, 2020
Borates are boron-containing oxyanions while boron itself often occurs in nature as borate minerals or borosilicates. Borates are derivatives of boric acid, B(OH)3 whose acidity is because of its reaction with OH− from water, forming the tetrahydroxyborate complex (B(OH4−) and releasing the corresponding proton left by the water autoprotolysis [805]: B(OH)3+2H2O⇌B(OH)4−+H3O+pKa=8.98[1057] Boric acid undergoes condensation reactions under acidic conditions to form polymerric oxyanions: 4B(OH)4−+2H+⇌B4O5(OH)24−+7H2O The tetraborate anion occurs in the mineral borax, Na2B4O7·10H2, as an octahydrate, Na2B4O5(OH)4·8H2O. A number of borates arise from treating boric acid or boron oxides with metal oxides [807]. Over 150 borate minerals are known and their deposits are associated with volcanic activity and arid climates. Only four of them are of industrial importance: the sodium borates tincal and kernite, the calcium borate colemanite and the sodium-calcium borate ulexite.
Studies on the effect of heterogeneous catalysts on the hydrothermal liquefaction of sugarcane bagasse to low-oxygen-containing bio-oil
Published in Biofuels, 2019
Gopalakrishnan Govindasamy, Rohit Sharma, Sunu Subramanian
Heterogeneous catalysts have been studied for HTL. Tekin et al. [16] studied the HTL of beech wood which yielded bio-oil at 41% containing 33.6% oxygen in the presence of calcium borate mineral catalyst. In the presence of Fe powder catalysts, Paulownia wood yielded 36% bio-oil containing 19.4% oxygen [8]. Zeolite Beta, Y and ZSM-5 were studied as catalysts for HTL of pine sawdust [17] and it was found that the yield of bio-oil was less over zeolite catalyst due to a higher yield of solid residue. Cheng et al. [18] studied HZSM-5 and Ni/HZSM-5 for the HTL of pine sawdust and found that Ni/HZSM-5 yielded bio-oil containing less oxygenates and more hydrocarbons owing to its deoxygenation activity. Nazari et al. [19] studied a range of homogeneous, heterogeneous and combined homo- and heterogeneous catalysts for HTL of birch wood sawdust and found that KOH, K2CO3 and colemanite yielded the highest amount of bio-oil and the least solid residue. Zhou et al. [2] reviewed the various catalytic processes for the conversion of lignocellulosic biomass to fuelsand emphasised the importance of the development of a heterogeneous catalyst system for HTL with deep deoxygenation activity to obtain bio-oil with less oxygen. Keeping this in view, in this study, Co-, Mo-, Fe- and Ti-substituted MCM-41, their oxides and mixed metal oxides of Fe-Mo, Fe-Co, Co-Mo and Ti-Zr were evaluated as catalysts for the HTL of sugarcane bagasse in the presence of CO and H2 as a process gas to obtain the maximum yield of bio-oil with the least oxygen content.
Borate mineral loading into acrylic bone cements to gain cost-effectivity, enhanced antibacterial resistivity, and better cellular integration properties
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Mesut Kaplan, Erdoğan Özgür, Orkun Ersoy, Lokman Kehribar, Neslihan İdil, Lokman Uzun
Antibacterial activity of sodium borate- and calcium borate-loaded cements were investigated and analyzed by agar disc diffusion assay. The results were evaluated according to the presence of inhibition zones formed by semi-spherical bone cement samples (Supplementary Figure S2), whereas antibacterial resistivities of sodium borate- and calcium borate-loaded cements were summarized in Table 2 as well. As can be seen from this table, the rates of bacterial growth reduced with the increasing amounts of sodium and calcium borate minerals. It is noteworthy to say that both of the sodium borate- and calcium borate-loaded cements have unique antibacterial performance against S. aureus which is one of the most common factors of bone defects when compared with those of vancomycin and gentamycin discs (Supplementary Figure S2). Similar to the antibacterial activity against gentamycin-susceptible S. aureus, sodium borate- and calcium borate-loaded cements demonstrated significant antibacterial activity against vancomycin-susceptible E. faecalis. In this respect, sodium borate- and calcium borate-loaded cements have been introduced as important antibacterial materials for preventing E. faecalis infections. Especially, sodium borate-loaded cements have higher antibacterial activity than that of calcium borate-loaded cements. Herein, it should be mentioned that calcium borate mineral showed a better structural integrity with commercial bone cement; however, sodium borate mineral resulted in a btter antibacterial resistivity. It could be concluded that prepared sodium borate- and calcium borate-loaded cements could be promising materials and recommendable as good alternatives to vancomycin- and/or gentamycin-loaded materials. Especially, sodium borate-loaded cements have been useful for preventing the infection occurrence originating from microbial contamination during surgical applications and other latent infections. Obtained results indicated that both of the sodium borate- and calcium borate-loaded bone cements showed appreciable antibacterial activity against E. faecalis and S. aureus strains by remarkably decreasing bacterial growth.