N. Rajagopalan

Sorption properties of greenwaste biochar for two triazine pesticides

Biochar is a carbon-rich product generated from biomass through pyrolysis. This study evaluated the ability of an unmodified biochar to sorb two triazine pesticides - atrazine and simazine, and thereby explored potential environmental values of biochar on mitigating pesticide pollution in agricultural production and removing contaminants from wastewater. A greenwaste biochar was produced by heating waste biomass under the oxygen-limited condition at 450 degrees C. The effects of several experimental parameters, including biochar particle size, contact time, solid/solution ratio, and solution pH on the sorption of atrazine and simazine were comprehensively investigated. The biochar with small particle size needed less time to reach sorption equilibrium. The sorption affinity of the biochar for the two pesticides increased with decreasing solid/solution ratio. The sorbed amounts (C(s)) of atrazine and simazine increased from 451 to 1158 mg/kg and 243 to 1066 mg/kg, respectively, when the solid/solution ratio decreased from 1:50 to 1:1000 (g/mL). The sorption of the biochar for both pesticides was favored by low pH. The sorption isotherms of atrazine and simazine on the biochar are nonlinear and follow a Freundlich model. When atrazine and simazine co-existed, a competitive sorption occurred between these two pesticides on the biochar, reflecting a decrease in sorption capacity (K(f)) from 435 to 286 for atrazine and from 514 to 212 for simazine. Combined adsorption and partition mechanisms well depicted sorption of atrazine and simazine on carbonized and noncarbonized fractions of the biochar in the single-solute and co-solute systems.

Deacidification of soybean oil by membrane technology

After extracting free fatty acids (FFA) from a model crude vegetable oil with methanol, FFA were separated from methanol by nanofiltration. Of the several commercially available membranes that were evaluated, the best resulted in FFA rejection of >90% and flux of >25 Lm−2h−1. A combination of high-rejection and low-rejection membranes resulted in a retentate stream of 35% FFA and a permeate stream with less than 0.04% FFA, which can be recycled to the extractor. No alkali is required, no soapstock is formed, and almost all streams within the membrane process are recycled with little discharged as effluent.

Pervaporation of grape juice aroma

Abstract Pervaporation of a model flavor compound of concord grapes (methyl anthranilate) was evaluated with several membranes. Flux and selectivity decreased linearly with increase in downstream pressure, and increased with temperature. With a polydimethoxylsiloxane-polycarbonate membrane, increasing the feed concentration from 20 to 200 ppm did not affect the flux (55 g m−2 h−1), but decreased the selectivity from 10 to 4. The presence of ethanol in the feed solution lowered separation factors and increased total flux. A polyether block amide membrane generally gave higher flux and better selectivity. Experiments with commercial grape essence confirmed the excellent potential of pervaporation for the production of highly enriched flavors.

Chemical and Biological Characterization of Wastewater Generated from Hydrothermal Liquefaction of Spirulina

Hydrothermal liquefaction (HTL) is an attractive method for converting wet biomass into petroleum-like biocrude oil that can be refined to make petroleum products. This approach is advantageous for conversion of low-lipid algae, which are promising feedstocks for sustainable large-scale biofuel production. As with natural petroleum formation, the water in contact with the produced oil contains toxic compounds. The objectives of this research were to: (1) identify nitrogenous organic compounds (NOCs) in wastewater from HTL conversion of Spirulina; (2) characterize mammalian cell cytotoxicity of specific NOCs, NOC mixture, and the complete HTL wastewater (HTL-WW) matrix; and (3) investigate mitigation measures to reduce toxicity in HTL-WW. Liquid-liquid extraction and nitrogen-phosphorus detection was used in conjunction with gas chromatography-mass spectrometry (GC-MS), which detected hundreds of NOCs in HTL-WW. Reference materials for nine of the most prevalent NOCs were used to identify and quantify their concentrations in HTL-WW. Mammalian cell cytotoxicity of the nine NOCs was quantified using a Chinese hamster ovary (CHO) cell assay, and the descending rank order for cytotoxicity was 3-dimethylamino-phenol > 2,2,6,6-tetramethyl-4-piperidone > 2,6-dimethyl-3-pyridinol > 2-picoline > pyridine > 1-methyl-2-pyrrolidinone > σ-valerolactam > 2-pyrrolidinone > ε-caprolactam. The organic mixture extracted from HTL-WW expressed potent CHO cell cytotoxic activity, with a LC(50) at 7.5% of HTL-WW. Although the toxicity of HTL-WW was substantial, 30% of the toxicity was removed biologically by recycling HTL-WW back into algal cultivation. The remaining toxicity of HTL-WW was mostly eliminated by subsequent treatment with granular activated carbon.

Ingredient-Wise Study of Flux Characteristics in the Ceramic Membrane Filtration of Uncontaminated Synthetic Metalworking Fluids, Part 1: Experimental Investigation of Flux Decline

Membrane Filtration (MF) technology can remove microbes, particulates, and tramp oils that contaminate metalworking fluids (MWFs). Consequently MF has the potential to reduce health risks and extend MWF life in the machine tool industry. This research assesses the productivity of ceramic membrane filters during filtration of synthetic MWFs and examines the contribution of MWF chemical ingredients to productivity decline. The majority of the chemistry comprising typical synthetic MWFs has negligible impact on MF productivity. However, specialty additives such as lubricants, defoamers, and biocides can significantly reduce MF productivity. Results show that slight variations in formulation can dominate the productivity of the process. Specialty additives can also impart residual effects on the membrane that adversely impact productivity in subsequent applications of the ceramic membrane.

Process optimization in ultrafiltration : flux-time considerations in the purification of macromolecules

Abstract An empirical model was developed to describe the flux of a complex milk protein suspension under ultrafiltration and diafiltration conditions. Flux decreased during ultrafiltration, but increased during diafiltration as the permeable solids concentration decreased. The “gel” model based on film theory was modified to describe the flux in terms of both retained and permeable solutes. The least-time processing strategy for a given end product concentration was also modelled and identified for this protein system. In general, ultrafiltration followed by diafiltration is best if protein purification is the goal.

Recovery of diacetyl by pervaporation

The recovery and concentration of diacetyl from aqueous solutions by pervaporation was studied with a PDMS-PC membrane at 33°C. Flux decreased with partial pressure and increased with temperature and concentration of diacetyl. Selectivity values greater than 30 were obtained. Whey permeate components had no effect on pervaporation parameters.

Ingredient-wise study of flux characteristics in the ceramic membrane filtration of uncontaminated synthetic metalworking fluids, Part 2 : Analysis of underlying mechanisms

Part 2 of this paper reveals the predominant mechanism of flux decline during microfiltration of the synthetic MWF described in Part 1 of this paper. An analysis of flux data obtained during the experimental investigation suggests that adsorptive interactions occur at the membrane surface. Field Emission Environmental Scanning Electron Microscopy (FE-ESEM) images of aluminum oxide membranes after MWF microfiltration illustrate that adsorption leads to a reduction in pore diameter that serves to reduce flux. The majority of the adsorption is accounted for by a single lubricant additive in the MWF formulation. FE-ESEM images also reveal that the mechanism of flux decline for the defoamer varies depending on the presence of lubricant additive in solution. In the absence of lubricant additive, the defoamer forms a cake layer at the membrane surface. In the presence of the lubricant additive, the defoamer adsorbs to the surface of the membrane with the lubricant additive to constrict pores. In contrast to the lubricant additive and defoamer, base fluid flux decline observed after specialty additive exposure cannot be accounted for by adsorption leading to pore constriction.

Microfiltration of Polyoxyalkylene Metalworking Fluid Lubricant Additives Using Aluminum Oxide Membranes

Microfiltration is capable of reducing health hazards and environmental pollution associated with metalworking fluids (MWFs) by enabling recycling and microbial removal. This paper investigates chemical characteristics of MWFs that can lead to flux decline during microfiltration using aluminum oxide membranes by studying the family of polyoxyalkylene diblock copolymers comprised of ethylene oxide and propylene oxide. These copolymers are commonly used as lubricant additives in metalworking fluids and serve as a model for beginning to understand the relationship between metalworking fluid formulation and microfiltration flux. It is found that increasing the hydrophobic content of the copolymers can lead to reduced flux. Anionic modification and increasing molecular weight of the copolymers can also lead to reduced flux. Insufficient cleaning of anionic copolymers from the membrane leads to pH-dependent flux of deionized water during subsequent filtration. The pH-dependence of flux arises due to swelling caused by electrostatic repulsions between the aluminum oxide surface and anionic copolymers that remain adsorbed to the surface of the membrane. This swelling serves to resist permeate flow above the isoelectric point of aluminum oxide. This phenomenon is observed directly using Field Emission Environmental Scanning Electron Microscopy (FE-ESEM).

Development of a Novel Metalworking Fluid Engineered for Use With Microfiltration Recycling

Membrane microfiltration is a promising technology that has been shown to extend metalworking fluid (MWF) life by eliminating contaminants while allowing the fluid to stay in use. However, the efficacy of this technology is compromised by the clogging of the filter pores in a process known as membrane fouling. In this paper the fouling issue is addressed by the development of a semi-synthetic MWF specifically designed to reduce fouling of microfiltration membranes. The composition of the designed MWF is discussed and compared with a commercial MWF. Cross-flow microfiltration fouling tests were carried out in low pressure, high velocity conditions on ceramic α-alumina membranes. Several common MWF components are shown not to be factors of membrane fouling on these membranes. The flux of the designed fluid was found to reach an immediate steady-state at about twice the value of the steady-state flux of the tested commercial fluid. SEM imaging was used to further evaluate membrane fouling by each fluid. The machining capabilities of the designed fluid were examined in terms of cutting forces and machining temperature.Copyright