Formation Of Boric Acid Research Articles

Sustainable treatment of boron industry wastewater with precipitation-adsorption hybrid process and recovery of boron species

Boron removal from wastewater has been investigated by using various processes, including ion exchange resins, membrane processes and adsorption. Each method has various advantages and disadvantages, but most produce excessive waste in addition to high operational costs. Therefore, more sustainable methods are required for wastewater containing high concentrations of boron. In this study, a sustainable treatment process was developed for wastewater containing high concentrations of boron. This study investigated the removal of boron from wastewater by Al(OH)3 sorption. The reuse of adsorbent (Al(OH)3) and the potential recovery of boric acid was the main goal of the study. It was observed that although lower concentrations of boron were obtained at pH 10.5 (980 mg/L and 635 mg/L at pH of 9.0 and 10.5, respectively), the amount of sorbed boron at pH 9 was substantially higher (94.7 mg B/g Al(OH)3 and 27.8 mg B/g Al(OH)3 at pH of 9.0 and 10.5, respectively). This was attributed to the higher initial boron concentrations and the formation of boric acid and polyborate complexes at pH 9.0. Results showed that polyborate species sorption was an outer sphere complex formation, which led to the desorption of boron as pH lowered. Adsorbed boron species to Al(OH)3 could effectively be desorbed at low pH values (pH<5.0); which allows Al(OH)3 to be used in successive adsorption studies. Approximately 55% of boron recovery from pretreated wastewater was possible with the effective reuse of adsorbent. A net profit of 2.85 $/m3 could be obtained based on the amounts of chemical consumptions and boron recovery.

Aggregation of Gold Nanoparticles Caused in Two Different Ways Involved in 4-Mercaptophenylboronic Acidand Hydrogen Peroxide.

The difference in gold nanoparticle (AuNPs) aggregation caused by different mixing orders of AuNPs, 4-mercaptophenylboronic acid (4-MPBA), and hydrogen peroxide (H2O2) has been scarcely reported. We have found that the color change of a ((4-MPBA + AuNPs) + H2O2) mixture caused by H2O2 is more sensitive than that of a ((4-MPBA + H2O2) + AuNPs) mixture. For the former mixture, the color changes obviously with H2O2 concentrations in the range of 0~0.025%. However, for the latter mixture, the corresponding H2O2 concentration is in the range of 0~1.93%. The mechanisms on the color change originating from the aggregation of AuNPs occurring in the two mixtures were investigated in detail. For the ((4-MPBA + H2O2) + AuNPs) mixture, free 4-MPBA is oxidized by H2O2 to form bis(4-hydroxyphenyl) disulfide (BHPD) and peroxoboric acid. However, for the ((4-MPBA+AuNPs) + H2O2) mixture, immobilized 4-MPBA is oxidized by H2O2 to form 4-hydroxythiophenol (4-HTP) and boric acid. The decrease in charge on the surface of AuNPs caused by BHPD, which has alarger steric hindrance, is poorer than that caused by -4-HTP, and this is mainly responsible for the difference in the aggregation of AuNPs in the two mixtures. The formation of boric acid and peroxoboric acid in the reaction between 4-MPBA and H2O2 can alter the pH of the medium, and the effect of the pH change on the aggregation of AuNPs should not be ignored. These findings not only offer a new strategy in colorimetric assays to expand the detection range of hydrogen peroxide concentrations but also assist in deepening the understanding of the aggregation of citrate-capped AuNPs involved in 4-MPBA and H2O2, as well as in developing other probes.

The Tribological Performances of the Boron Carbide Films Tested under Wet Air and Wet N2 Conditions

In the previous literatures, the friction reduction of boron carbide (B4C) with the increasing relative humidity was mainly attributed to the formation of boric acid during the friction tests. In the present investigation, however, low friction coefficient was obtained under wet air (85% RH) without the formation of boric acid, suggesting that there is another low friction mechanism. Furthermore, low friction coefficient was also achieved under wet N2 (85% RH, without O2) without the formation of boric acid, implying that the core factor for the friction reduction is water vapor rather than oxygen. Therefore, we infer that the adsorption of H2O on the passivated boron carbide surface is the main reason for the reduction of friction coefficient. It should be noted that friction coefficients under wet air were lower than that under wet N2, which demonstrates that O2 plays a secondary role to reduce friction coefficient.

Effects of relative humidity on tribological properties of boron carbide coating against steel

Boron carbide coatings of 100 nm thick were synthesized on silicon substrate by DC magnetron sputtering using B 4C target with a mixture of Ar and methane (CH 4 at 1.2 vol.%) as processing gases. Tribological properties of the coating were studied in relation to the effects of relative humidity (RH). Reciprocating wear tests using 3 mm diameter steel balls as a counterpart were carried out at three relative humidity conditions. Confocal microscopy was used to observe worn surfaces and the wear scars on the steel balls. Elemental composition of the coating and worn surfaces were characterized using X-ray photoelectron spectroscopy and Auger electron spectroscopy. The tribological properties of boron carbide coating slid against steel ball were strongly affected by relative humidity. Lower and steady friction coefficient and higher wear resistance for both the coating and the steel ball were achieved at higher relative humidity. At high RH, tribochemical reaction occurred in the sliding surfaces, forming boric acid and carbon in a graphitic form on the worn surface of coating and a soft layer on the ball surface. The formation of boric acid on boron carbide coating combined with graphite structure led to the low and stable friction of boron carbide coating in medium and high relative humidity conditions. Smooth layer was formed on the worn surface of the steel ball at high relative humidity due to the tribochemical reaction. Low and steady value of friction coefficient and reduction of wear loss of both steel ball and boron carbide coating were attributed to the formation of the soft layer.

Elastic modulus of amorphous boron suboxide thin films studied by theoretical and experimental methods

Boron suboxide BOx thin films have been deposited on Si (100) by reactive rf magnetron sputtering of B powders in an Ar/O2 atmosphere. Elastic recoil detection analysis and x-ray diffraction were used to study the influence of the O incorporation on the film composition and structure and relate them to mechanical properties, which were evaluated by nanoindentation. As x in BOx was increased from 0.08 to 0.18, the elastic modulus of the x-ray amorphous films decreased from 273 to 231 GPa, by 15%. This can be understood using classical molecular dynamics (MD) with a Buckingham-like interaction potential: The increase in the O concentration and corresponding formation of B–O bonds, shown to be longer than the B–B bonds, resulted in larger ionic contributions as well as a density reduction. This increased ionicity was responsible for the observed decrease in elastic modulus. As even more O was incorporated (x&amp;gt;0.18), the H concentration increased, exceeding 0.3 at. %. This may cause the formation of boric acid (H3BO3) as a result of the chemical reaction with H2O upon atmosphere exposure. The presence of van der Waals and hydrogen bonding, associated with H3BO3 formation, provides a reasonable explanation for the extensive decrease in elastic modulus from 231 to 15 GPa, by 94%. The parameterization for the Buckingham-like interaction potential, introduced in this study, can be used for MD simulations of amorphous BOx systems without H3BO3.

Stability of Nextel fibres in aqueous environments detected by photoacoustic Fourier transform infrared spectroscopy

Photoacoustic Fourier transform infrared spectroscopy was utilized to monitor the effect of basic, acidic and neutral aqueous environments on the stability of Nextel ceramic fibres. Such treatments led to the removal of a residual hydrocarbon phase from the fibre and formation of boric acid. The presence of boric acid upon the treatment does not effect the stability of the fibre at high temperatures. At high temperatures, B(OH) 3 is apparently converted to B 2O 3, this process enhancing the surface stability and improving the adhesive properties of fibres to the polymer matrix.