Removal of API's (Active Pharmaceutical Ingredients) from Organic Solvents by Nanofiltration

Abstract

The removal of 5 specific active pharmaceutical ingredients (API's) with molecular weight of 189, 313, 435, 531, and 721, respectively, from toluene, methylene chloride, and methanol was studied by using solvent resistant nanofiltration. Three membranes of the StarMem series (120, 122, and 228), with cut‐off values of 200, 220, and 280 respectively, were used in the experiments. Although the rejections expected from the size difference between solutes and membrane pores are high, the results largely depended on the solvent used. For toluene, rejections were rather small, due to the low molecular weight of the solutes of interest (all API's except for the largest compound). Modelling of the rejection curve showed that the minimum molecular weight of a solute to obtain a rejection of 90% in toluene with the membranes used, is ca. 600. The application in methylene chloride was unsuccessful due to partial dissolution of the membrane top layer; other polymeric membranes such as the Solsep series might be more successful. The rejections in methanol were sufficiently high (>90%) to allow implementation: the rejection can be significantly increased by using a module design with double membrane passage and recirculation of the retentate, as was calculated from mass balances. A comparison of a (single pass) nanofiltration system with a throughput distillation unit, currently in use, showed that the energy consumption is 200 times lower in the nanofiltration system.     

Synthesis and Metal‐ion Binding Properties of New N2S4O2‐ and N2S5O2‐Donor Macrocycles

Abstract

Synthetic procedures for new mixed‐donor macrocycle compounds were reported. The macrocyclic compounds were used in solvent extraction metal picrates such as Ag⁺, Hg²⁺, Cd²⁺, Zn²⁺, Cu²⁺, Ni²⁺, Mn²⁺, Pb²⁺, and Co²⁺. The metal picrate extractions were investigated at 25±0.1°C with the aid of UV‐visible spectrometry. It was found that 6,7,9,10,12,13,23,24‐octahydro‐19H,26Hdibenzo[h,t](1,4,7,13,16,22,10,19) dioxatetrathiadiazasiclotetracosine‐20,27(21H,28H)‐dione showed selectivity towards Ag⁺, Hg²⁺, and Cd²⁺ among the other metals. The extraction constants (Log K_ex) and complex compositions were determined for the Ag⁺ and Hg²⁺ complexes for this compound and 9,10,12,13,23,24,26,27,29,30‐decahydro‐5H,15H‐dibenzo‐[h,w][1,4,7,13,16,19,25‐,10,22] dioxapentathiadiazacycloheptacosine‐6,16(7H,17H)‐dione.     

Performance of Granular Activated Carbon (GAC) Adsorption and Biofiltration in the Treatment of Biologically Treated Sewage Effluent

Abstract

In this study, the performance of GAC adsorption and biofiltration systems in treating biological treated sewage effluent (BTSE) was evaluated in terms of organic removal efficiency, organic fractions, and molecular weight distribution (MW) of organic matter (OM) removed. The GAC biofilter removed 23.5% and 61% of the hydrophobic fractions and hydrophilic fractions of OM in the BTSE respectively. MW distribution studies of GAC filter and GAC adsorption revealed the following: Hydrophobic fraction of the effluent showed a peak at 345 dalton after GAC biofiltration and 256 dalton after GAC adsorption, whereas, with hydrophilic fractions, peaks at 46,178 and 345 daltons were observed after GAC biofiltration and peaks at 46,178 and 256 daltons after GAC adsorption. Transphilic fraction showed the peaks at 12,783 dalton with GAC biofiltration, and 1,463 dalton with GAC adsorption. The performance of the GAC biofilter was successfully mathematically modelled.     

Continuous Cloud Point Extraction of Volatile Organic Contaminants from Wastewater in a Multi-Stage Rotating Disc Contactor: Effect of Structure and Concentration of Solutes

Abstract

Cloud point extraction (CPE) has been successfully scaled up to continuously remove aromatic contaminants from wastewater in a multi-stage rotating disc contactor (RDC) using t-octylphenolpolyethoxylate. The extraction performances for the removal of organic solutes with different structures and degrees of hydrophobicity were compared here for both batch and continuous CPE. Included are the volatile aromatics benzene, toluene, and ethylbenzene; volatile chlorinated compounds dichloroethane, trichloroethylene, and tetrachloroethylene; and non-volatile phenolics phenol, o-cresol, and catechol. The higher the K_ow (octanol-water partition coefficient) or hydrophobicity of the solutes, the better the extraction due to the greater affinity of solutes to solubilize into micelles. The empirical linear correlations between log K_ow, log (solute partition ratio), and log (height of transfer unit or HTU) were developed. Toluene is used as a model solute for the study of effect of initial solute concentrations in the continuous RDC. The extraction ability decreases as the concentration of toluene in the wastewater increases mainly due to coacervate entrainment into the overhead effluent.     

Effects of Operating Modes on the Rejection Behavior using Ceramic Membranes

Abstract

Fouling generally occurs above the so-called “critical flux,” below which steady-state membrane permeability is assumed to be attainable. Operation at sub-critical fluxes can thus be used to minimize membrane fouling. However, rejection behavior may be affected as a consequence of operating within this sub-critical mode that sustains the desirable permeate flux. In this study, the effluent from a synthetic activated sludge production process was used in the assessment of the performance of membrane microfiltration, as a pretreatment in desalination for wastewater reuse. The critical flux was identified using the step-by-step technique. Different operating regimes i.e. above and below the critical flux were used to assess the relationship between solute rejection and membrane fouling. When operating at sub critical mode, rejection was constant even under increasing transmembrane pressure (TMP). This arises mainly from the back transport of particles in the absence of cake formation. Beyond the critical regime, cake formation occurred and rejection increased with increasing TMP. At the critical regime, a decline in rejection was obtained. This rejection behavior was consistent over the three pore sizes that were investigated. Increasing the pore size appears to decrease the rejection at both regimes. This is because larger pore size allows the transmission of smaller particles and a less compact cake formation under and above the critical flux regime respectively. It appears from this study that one may be able to use rejection behavior to confirm and determine the critical flux and adds to the confidence of using the step-by-step method to determine the critical flux.     

Modeling of Nanofiltration Process for Solvent Recovery from Aqueous Ethanol Solution of Soybean Isoflavones

Abstract

In this paper, the feasibility of recovering the solvent from the aqueous ethanol solution of soybean isoflavones with nanofiltration (NF) was studied. Five commercially available polymeric NF membranes were employed and STARMEM? 122 showed acceptable flux and high retention. The central composite design (CCD) of the response surface methodology (RSM) was applied to model the effects of temperature, pressure, and feed concentration on the permeate flux and the total soybean isoflavone retention. The results indicate that the developed models were in good agreement with the experimental results and they can be used to predict this NF process.     

Treatment of Fumaric Acid Wastewater Using Integrated Process of Hollow-Fiber Supported Liquid Membrane-Strip Dispersion with Reverse Osmosis

In this paper, the integrated process of series connected hollow-fiber supported liquid membrane-strip dispersion (HFSLM-SD) with reverse osmosis (RO) was designed and used to recover fumaric acid (FA) from waste effluents and treat FA wastewater. The results showed that FA could be almost completely recovered by this integrated process, and TOC of wastewater finally decreased to the environment acceptable level. In addition, the continuous operation of wastewater treatment was implemented by the integrated process. After FA wastewater was extracted by six series connected HFSLM-SD modules, its TOC decreased from 35625 mg/L to 1000 mg/L, and the TOC removal rate reached 97.17%. Then the effluent from HFSLM-SD was further treated by RO, and TOC of permeate in RO was below 100 mg/L. The total TOC removal rate of the integrated process was as high as 99.7%. Furthermore, the effect of the osmotic pressure of RO process on TOC in the feed was obtained. The investigation of RO membrane fouling revealed that washing process was necessary because of the serious fouling in RO system.     

Separation of Copper and Zinc by Solvent Extraction During Reprocessing of Flotation Tailings

Results from the solvent extraction of copper and zinc from pregnant solutions after bioleaching of re-floated tailings from the Kipushi concentrator in DR of Congo are presented. LIX984N has been used as extractant for copper, while D2EHPA as such for zinc, following prior removal of the ferric iron via precipitation. The McCabe-Thiele diagrams constructed for Cu and Zn extraction have theoretically suggested the need for two stages for copper and one for zinc. Stripping these metals to the aqueous phase by sulphuric acid has yielded rich electrolytes with 48.5 g/L copper and 85.5 g/L zinc. Thus, copper and zinc could be further recovered from the stripped solutions by electrolysis.     

Studies on the Separation and Recovery of Uranium from Phosphoric Acid Medium Using a Synergistic Mixture of (2-Ethylhexyl)phosphonic Acid Mono 2-Ethyl Hexyl Ester (PC-88A) and Tri-n-octylphosphine Oxide (TOPO)

This paper deals with studies on the extraction of uranium(VI) from phosphoric acid medium using (2-ethylhexyl)phosphonic acid mono 2-ethylhexyl ester and tri-n-octylphosphine oxide individually as well as from their synergistic mixture. Different extraction parameters were investigated. With an increase in phosphoric acid concentration in the aqueous phase, the distribution ratio (Du) was found to decrease in all the cases. Synergism was observed when a mixture of PC-88A and TOPO was used. The synergistic mixture in the mole ratio of 4:1 (1.80 M PC-88A: 0.45 M TOPO) in xylene was found to be most suitable for uranium extraction. Among the various strip liquors used, 5% (w/v) solution of (NH₄)₂CO₃ was found to be the most suitable. Using a mixture of 1.8 M PC-88A and 0.45 M TOPO as the extractant system and 0.5 M ammonium carbonate as the stripping agent, uranium recovery was found to be better than 97% ± 3% in multiple contacts, (n = 2) from actual Davies Gray Waste while in case of wet phosphoric acid more than 52% ± 3% (n = 3) only could be recovered where n is the number of contacts.     

Studies on Development on Methodology for Extraction of Phenolic Compound from Hydro-Alcoholic Wood Extracts

This article presents results on the liquid-liquid extraction studies for the separation of tannic acid from aqueous and hydro-alcoholic medium. These liquid-liquid extraction studies aim to investigate the suitable hydrophobic solvent or solvents combination and to optimize the extraction conditions for the quantitative separation of tannic acid from aqueous and hydro-alcoholic feed. A mixture of hexanol and octanol is found to be most suitable for the quantitative extraction of tannic acid from aqueous feed solution. One hour equilibration time was enough to reach equilibrium. With increase in tannic acid concentration from 10 mg · L^?1 to 900 mg · L^?1 in the feed solution, the extraction of tannic acid was found to be decreasing. The concentration of ethanol plays an important role in controlling the solubility of feed in hydrophobic solvent. The suitable solvent combination was tested for the selectivity for individual polyphenol from a mixture of tannic acid and Epi-catechin and it was found that a combination of hexanol and octanol was good for tannic acid extraction whereas decanol was more selective for Epi-catechin extraction.