Enhancing Stability and Tooth Bleaching Activity of Carbamide Peroxide by Electrospun Nanofibrous Film

Carbamide peroxide (CP) possesses a strong tooth bleaching activity, however, its clinical application is limited because of its instability in aqueous formulations. This study explores the improvement of CP stability and bleaching activity by loading CP in electrospun nanofibrous film (ENF). Polyvinylalcohol, polyvinylpyrrolidone, and silica were used as components for core-based nanofibers of ENF. Electrospinning feed aqueous solutions (EFASs) were developed for preparing CP loaded ENF (CP-ENF). Stability of CP in EFASs is significantly higher than in pure water. The highest stability of CP is found in PPS-CP3, composed of 0.5% CP, 5.5% polyvinylalcohol, 3% polyvinylpyrrolidone, and 1% silica. The results from X-ray diffraction indicate that CP is dispersed as a non-crystalline form in CP-ENFs. CP and the compositions of EFASs play a major role on characteristics and bleaching efficiency of CP-ENFs. Drug release of CP-ENFs is the first order kinetics. CP-ENF obtained from PPS-CP3 shows the highest drug entrapment efficiency, high adhesion, and suitable sustained release. Drug release mechanism is along with anomalous transport according to Korsmeyer–Peppas model. In an ex vivo study using human teeth, it shows the highest bleaching efficiency among the others. Therefore, CP-ENF obtained from PPS-CP3 is a promising ENF for clinical use.

PREPARATION OF ACTIVATED CARBON FROM TEAK LEAVES FOR THE DECOLORIZATION OF PALM OIL

The bleaching efficiency of activated carbon prepared from teak leaves was investigated for the removal of pigments from palm oil. The adsorbents were activated using KOH and FeCl3 as activating agents. The effects of adsorbent dosage (2% - 6 %), contact time (15 min. – 90 min.) and temperature (30 °C – 80 °C) were studied, while the unactivated adsorbent was used as standard. The ash content, moisture content, volatile matter content, and fixed carbon content were determined and the adsorptive bleaching of palm oil investigated using 1.2 g activated carbon with 20 g crude palm oil. Bleaching efficiency was observed to be 93.09 % and 96.68 % for the KOH and FeCl3 activated adsorbent respectively, while the unactivated adsorbent was observed to have a bleaching efficiency of 89.21 %. The optimum bleaching efficiency was observed at a temperature of 70 °C, adsorbent dosage of 6 %, and contact time of 90 min. Results obtained suggests that teak leaves can be a source of low-cost adsorbent for the removal of pigments from palm oil which is of great relevance in obtaining a clean environment.

PREPARATION OF ACTIVATED CARBON FROM TEAK LEAVES FOR THE DECOLORIZATION OF PALM OIL

The bleaching efficiency of activated carbon prepared from teak leaves was investigated for the removal of pigments from palm oil. The adsorbents were activated using KOH and FeCl3 as activating agents. The effects of adsorbent dosage (2% - 6 %), contact time (15 min. – 90 min.) and temperature (30 °C – 80 °C) were studied, while the unactivated adsorbent was used as standard. The ash content, moisture content, volatile matter content, and fixed carbon content were determined and the adsorptive bleaching of palm oil investigated using 1.2 g activated carbon with 20 g crude palm oil. Bleaching efficiency was observed to be 93.09 % and 96.68 % for the KOH and FeCl3 activated adsorbent respectively, while the unactivated adsorbent was observed to have a bleaching efficiency of 89.21 %. The optimum bleaching efficiency was observed at a temperature of 70 °C, adsorbent dosage of 6 %, and contact time of 90 min. Results obtained suggests that teak leaves can be a source of low-cost adsorbent for the removal of pigments from palm oil which is of great relevance in obtaining a clean environment.

Clinical efficiency of a sodium perborate - hydrogen peroxide mixture for intracoronal non-vital teeth bleaching

Introduction/Objective. The aim was to evaluate initial efficiency of sodium perborate (tetrahydrate) and 30% hydrogen peroxide mixture for intracoronal non-vital teeth bleaching (?walking bleach? technique). Methods. Forty patients with discolored teeth were included in the study. Based on their history and clinical examination, causes of discoloration were classified as necrotic pulp, ?endo-sealer? or unknown. The ?walking bleach? technique was performed by applying sodium perborate (tetrahydrate) and 30% hydrogen peroxide mixture intracoronally to cavity dentin walls. The mixture was renewed in seven-day intervals. Tooth color was assessed visually before, during, and after the procedure using the Vita Classical shade guide (Vita Zahnfabrik, Bad Sackingen, Germany). Numerical values or shade guide units (SGU) were assigned to Vita shade tabs on a bright-dark scale. Analysis of variance, t-test, correlation and regression analysis were used to analyze the data (p < 0.05). Results. On average, 26 ? 9 days or 3?4 appointments were required for intracoronal bleaching to achieve the desired or best possible shade. Better clinical efficiency was found in the necrotic pulp group (17 ? 6 days; 8 ? 3 SGU) than in the ?endo-sealer? group (42 ? 13 days; 4 ? 2 SGU) (p < 0.05). Age significantly influenced bleaching efficiency (p < 0.05). There was no significant correlation between bleaching efficiency and initial shade (p > 0.05). Conclusion. Intracoronal, non-vital teeth bleaching (?walking bleach? technique) using sodium perborate (tetrahydrate) and 30% hydrogen peroxide mixture showed satisfactory clinical efficiency. Discoloration caused by pulp necrosis was treated more efficiently than that caused by endodontic sealers. Younger age had a positive effect and discoloration intensity had no effect on bleaching efficiency.

Modified hydrogen peroxide bleaching of bamboo chemo-mechanical pulp using aqueous alcohol media

The brightness of bleached bamboo chemo-mechanical pulp (CMP) is often too low to be used as a furnish in value-added paper products. In this study, preliminary optimization of various parameters of a modified hydrogen peroxide (H2O2) bleaching procedure for bamboo CMP pulps was performed using the inclusion of ethanol in the bleaching medium (IEBM). Compared with a conventional bleaching method, this modified process is aimed at improving bleaching efficiency and brightness ceiling of bamboo CMP with the proper usage of chemicals. The CMP was bleached to a brightness of 74.2% ISO at the usage level of 12% H2O2, which shows it increased by 7.4% ISO compared with the conventional method. For a brightness target of 72.0% ISO, bleaching with the IEBM method reduced the H2O2 consumption by approximately 60%. In addition, a higher activation energy of H2O2 for the IEBM method was calculated to be 23.3 kJ/mol, which was increased by 3.3 kJ/mol compared with the conventional method.

Additives to decrease cellulose chain scission during ozone bleaching of wheat straw pulp

The efficacy of different chemical additives like acetic acid, ammonium molybdate, diethylene triamine pentaacetic acid (DTPA), mannitol, methanol, per acetic acid (PAA), sodium hypochlorite (NaOCl) and sulfamic acid as carbohydrate protector during ozone bleaching of wheat straw pulp was studied. DTPA was found the most effective additive for ozone bleaching followed by the methanol. Using DTPA during ozone treatment improved the delignification efficiency by 13.8 %, bleaching efficiency by 19.8 %, selectivity of ozone by 124 % and reduced the chain scission number of glycosidic linkages in cellulose by 55.3 % compared to that of control. Ozone treatment along with DTPA reduced the Fe, Cu and Mn content in the pulp by 52 %, 27 % and 70 %, respectively. Use of methanol improved the delignification efficiency by 9.0 %, bleaching efficiency by 12.2 %, selectivity by 32.4 % and reduced the chain scission number by 22.2 % compared to that of control. The NaOCl was found to be the most effective for improving the delignification efficiency followed by PAA, they improved the delignification efficiency by 29.3 % and 27.3 %, respectively. The PAA improved the bleaching efficiency to a maximum of 39.9 % followed by 30.2 % with NaOCl.

Equilibrium, Kinetics and Thermodynamics of the Bleaching of Palm Oil Using Activated Nando Clay

The effectiveness of Nando clay in the bleaching of palm oil was studied in this work. The clay was prepared by activating it with hydrochloric acid. The bleaching was carried out at different temperatures, adsorbent dosage and particle sizes. The result suggests that increase in temperature and adsorbent dosage increases the bleaching efficiency while the increase in particle size decreases the bleaching efficiency. Both the pseudo-first-order and the pseudo-second-order kinetic models describe efficiently the experimental data of the bleaching process. Intra-particle diffusion though involved in the adsorptive bleaching mechanism, is not the sole rate-limiting step in the bleaching of palm oil with activated Nando clay. The equilibrium data were described better by Langmuir and Freundlich models. The enthalpy, entropy and activation energy were determined to be 6.127 KJ/mol, 3.982 KJ/mol and 15.281 KJ respectively. The free energy was found to vary between- 3.999 to- 3.760 KJ/mol. The result indicates that bleaching efficiency of up to 96% can be obtained with the activated clay as an adsorbent.

Improving the efficiency of hydrogen peroxide bleaching of chemimechanical pulp by continuous replenishment of bleaching chemicals

Hydrogen peroxide (H2O2) is commonly used to bleach chemimechanical pulp. A decrease in the concentrations of the bleaching reagents throughout the bleaching process results in low bleaching efficiencies. In this study, chemical solutions were continuously added into the pulp slurry during the bleaching process to maintain constant concentrations of H2O2 and total alkali in the bleaching system to improve bleaching efficiency. The results showed that when the H2O2 and total alkali concentrations were maintained at 4.5 g/L and 0.79 g/L, respectively, for 50 min, the bleaching efficiency reached 16.79 (Δ% ISO brightness/Δ% H2O2 consumed [on ovendry pulp]), which was significantly higher than 7.38 obtained by using the high-consistency bleaching method. The results confirmed that continuous replenishment of chemical solutions into the bleaching system to maintain the constant chemical concentrations improved the efficiency of H2O2 bleaching of the chemimechanical pulp.