Formulation and optimization of biological removal of flue gas pretreatment wastewater and sulfur recycling process by Box–Behnken design

The aim of this study was to investigate optimum conditions for biological removal of flue gas pretreatment wastewater and achieve maximum elemental sulfur yield. A three-factor, three-level Box–Behnken design was used to derive a second-order polynomial equation and construct contour plots to predict responses. The independent variables selected were hydraulic retention time (X1), inlet sulfate concentration (X2), and air flow (X3). Fifteen batches were done in a biological united system and evaluated for elemental sulfur yield (Y1). The transformed values of the independent variables and Y1 were subjected to a full-model second-order polynomial equation. The equation was modified based on Fisher's F- and probability P-values. The computer optimization process and contour plots predicted the values of independent variables X1, X2 and X3 (16 h, 1,348 mg L−1 and 165 L h−1 respectively), for maximized response of Y1. The experimental results at predicted conditions demonstrate that the modified model equation has good applicability to the practical system.

Prediction of response to sulfur by established Siratro/grass pastures in south-eastern Queensland

Dry matter responses by component species of 18 established, commercial Macroptilium atropurpureum cv. Siratrolgrass pastures to gypsum topdressing treatments (0 or 25 kg S/ha) were assessed from field experiments conducted over a four-year period in south-eastern Oueensland under rain-grown conditions. The objective was to establish diagnostic criteria for the assessment of sulfur status by relating pasture yields to agronomic attributes and soil and plant chemical tests. Beneficial responses to gypsum were small (maximum of 32% in Siratro) and restricted to fewer than 25% of sites, whereas at disadvantaged sites (28% of total), grass yields were more severely depressed than Siratro yields. It was not possible to predict these effects from past sulfur fertilizer history, Siratro percentage in the pasture, or pasture age. Significant correlations between Siratro relative yields (100 x yield without sulfur/yield with sulfur applied, attenuated at 100 for model fitting) and both soil sulfate and plant sulfur concentrations confirmed the predictive value of these laboratory data. For Siratro, best prediction of responsiveness was provided by sulfur concentrations in either whole tops (R2 = 0.65) or diagnostic samples (tips of runners back to the fifth to sixth fully expanded leaf; R2 = 0.65). Critical value for diagnostic samples was 0. 16% S while for whole tops of Siratro the value varied with mathematical model from 0.13 to 0. 15% S. Phosphate-extractable sulfate was the most effective soil test but irrespective of sampling depth, it accounted for less than 50% of the variation in Siratro relative yields. Whether sampled at 0- 10 cm or 0-90 cm, a critical range of 3-5 ppm phosphate-extractable sulfate was indicated for the Siratro component. Grass and total pasture relative yields were not correlated with the chemical tests employed.

Improved Adhesion of EPDM Sulfur Vulcanizates to RFL-Treated Fabrics

EPDM stocks containing 5-norbornene-2,3-dicarboxylic anhydride and cobalt naphthenate, when sulfur vulcanized onto RFL-treated fabrics, show a significant increase in peel adhesion properties. EPDM's containing ENB, as the termonomer, have been found to give the best results. The accelerator is an important part of the total adhesion system. Only the slower curing types are applicable, such as sulfenamides and thiazoles. Both soluble and insoluble sulfur yield equivalent adhesion properties, but the insoluble form has the advantage of producing a higher modulus stock. This adhesion system is applicable to only RFL-treated fabrics in which the latex is a styrene-butadiene-vinyl pyridine type. Reduction of compounded stock cost is possible by increased filler loadings or by the use of a skim coat technique, while still providing improved adhesion properties. Variations in both carbon black and oil levels produce corresponding changes in modulus development and curing time. These properties can be used to predict adhesion results.