Synthesis of bulk ion-imprinted polymers (IIPs) embedded with oleic acid coated Fe3O4 for selective extraction of hexavalent uranium

A selective and reliable method for the extraction of trace quantities of U(VI) by the use of a magnetic U(VI) ion-imprinted polymer (IIP) was developed. In this study, oleic acid (OA) coated magnetite nano-particles were incorporated into the cross-linked polymeric matrix of the selective sorbent, in order to gain the physical advantages of separating the polymers. Many physico-chemical factors influence the adsorption process; uranyl ion uptake ability based on these parameters was investigated. The optimum parameters obtained were sample pH 4,50 mg of the magnetic polymer, a contact time of 45 min and an initial U(VI) concentration of 2 mg·ℓ-1. The adsorption capacities for the magnetic NIP and IIP were found to be 0.95 mg·g1 and 1.21 mg·g-1, respectively. The adsorption behaviour of U(VI) in the presence of other competing metal ions onto the cross-linked magnetic polymers was also examined in binary mixtures and the order of selectivity was found to be U(VI) > Pb(VI) > Ni(II). The resulting magnetic nano-composite polymers were found to be stable up to the sixth cycle of use and reuse. The Freundlich adsorption model was used for the mathematical description of the adsorption equilibrium and the adsorption kinetic data fitted the pseudo-first-order model with R2 > 0.92.Keywords: Bulk, magnetic imprinted polymers, oleic acid, uraniu

Determination of Phenols in Water Samples using a Supported Liquid Membrane Extraction Probe and Liquid Chromatography with Photodiode Array Detection

A simple, selective and inexpensive miniaturized sample preparation method based on a supported liquid membrane extraction probe is described for the extraction and preconcentration in a single step of phenols in water samples. The phenols were extracted from 5 mL aqueous water samples into 0.4 mL aqueous acceptor  phase through the organic membrane. The organic membrane consisted of a porous PTFE membrane impregnated with undecane. In order to obtain a selective  extraction and enrichment of the phenols, the conditions were kept such that the phenols were non-ionized in the sample and ionized in the acceptor phase. This was achieved by pH adjustments in the sample and acceptor phases. The method was optimized for its extraction time, depth of the probe in the sample and   stirring speed. The detection limit ranged from about 4 μg L–1 for 2-chlorophenol and 2,4-dichlorophenol to 10 μg L–1 for 4-chlorophenol. The resulting enrichment  factors were about eight times for 2-chlorophenol and  2,4-dichlorophenol and four times for 4-chlorophenol. The sample preparation method was tested for the determination of phenols in river water samples and landfill leachate. Concentrations of phenols in river water were found to be in the range 4.2 μg L–1 for   2-chlorophenol to 50 μg L–1 for 4-chlorophenol. In landfill leachate, 4-chlorophenol was detected at a concentration of 80 μg L–1.KEYWORDS: Supported liquid membrane extraction probe, selectivity, chlorophenols, water samples

Selective adsorption of uranium (VI) on NaHCO3 leached composite γ-methacryloxypropyltrimethoxysilane coated magnetic ion-imprinted polymers prepared by precipitation polymerization

Ion imprinted nano-magnetic composite polymers for selective removal of hexavalent uranium were prepared by a precipitation polymerization technique in the presence of γ-methacryloxypropyltrimethoxysilane (γ-MPS) coated magnetite and other pre-polymerization reagents. The synthesized magnetic polymers were then leached with NaHCO3 to produce magnetic ion imprinted polymers (IIPs) with fabricated adsorption sites complementary to the uranyl ions in terms of size and shape. Several parameters were investigated to obtain conditions which gave the optimum adsorption of the uranyl onto the magnetic IIPs and their corresponding controls, magnetic ion non-imprinted polymers (NIPs). The optimum amount of magnetic sorbent, initial concentration and contact time were 50 mg, 2.5 mg L-1 and 45 min, respectively. The adsorption capacity of the magnetic IIP (1.15 ± 0.01 mg g-1) was higher than that of the magnetic NIP (0.93 ± 0.02 mg g-1). This indicated that the former had a somewhat higher affinity for U(VI) than the later. The magnetic polymers also displayed good selectivity of the order: U(VI) > Ni(II) > Mg(II). After six cycles of use, the magnetic polymers illustrated good stability and reusability.SP201

Determination of naproxen, ibuprofen and triclosan in wastewater using the polar organic chemical integrative sampler (POCIS): A laboratory calibration and field application

In this study, the occurrence in wastewater of two non-steroidal  anti-inflammatory drugs (NSAIDs), naproxen and ibuprofen, and one  personal care product, triclosan, was assessed using the polar organic  chemical integrative sampler (POCIS). The samplers were initially  calibrated in the laboratory to obtain sampling rates (Rs) for each target compound followed by deployment in the influent and effluent of  Goudkoppies and Northern Wastewater Treatment Plants (WWTPs), South Africa. Exposure was done for 14 days in 2012. High performance liquid chromatography (HPLC) system with ultraviolet (UV) and fluorescence (FLD) detectors was used to analyse POCIS extracts. Laboratory calibration of POCIS yielded Rs values for the three compounds that were between 0.087 and 0.383l.d-1 in quiescent conditions, and 0.125 and 0.936 l.d-1 in  stirred conditions. From the accumulated amounts in field-deployed  samplers, estimated freely dissolved concentrations of the studied compounds in wastewater influent ranged from 55.0 to 78.4 µg.l-1 and 52.3 to 127.7 µgl.-1 in Goudkoppies and Northern WWTPs, respectively. Average concentrations of these compounds in the treated effluent ranged from 10.7 to 13.5 µgl.-1 in Goudkoppies WWTP, and 20.4 to 24.6 µgl.-1 in Northern WWTP. Analyte removal efficiencies varied between 68 and 86% in Goudkoppies WWTP and 61 and 82% in Northern WWTP. Grab samples processed by SPE method yielded higher analyte concentrations (up to three-fold) as compared to POCIS-derived estimates. This  discrepancy was attributed to SPE's ability to extract both the free  dissolved, and particle sorbed fractions of the contaminants.Keywords: Polar organic chemical integrative sampler, pharmaceuticals and personal care products, wastewater, wastewater treatment plant

Use of compost bacteria to degrade cellulose from grass cuttings in biological removal of sulphate from acid mine drainage

The study focused on the use of compost bacteria to degrade cellulose from grass cuttings as energy and carbon sources for sulphate-reducing bacteria (SRB) in a biological reactor. The fermentation of grass cuttings was carried out by anaerobic bacteria isolated from compost, thereby producing volatile fatty acids (VFA) and other intermediates, which were used as carbon and energy sources for sulphate reduction by SRB. Grass was added daily to the reactor in order to obtain maximum production of chemical oxygen demand (COD) and VFA. The results indicated that daily addition of grass is essential for the efficient VFA production, sulphate reduction and for the cell growth of the microbial biomass. Sulphate reduction of 38% was achieved with an average reactor chemical oxygen demand/sulphate (COD/SO4) ratio of 0.56 mg/.. These results showed that 25 g of grass could produce enough VFA for a sulphate load of 25 g, which is a cost-effective method for sulphate removal

Coagulation efficiency of Dicerocaryum eriocarpum (DE) plant

A study was conducted to investigate coagulation efficiency of the plant Dicerocaryum eriocarpum (DE) in the removal of turbidity from raw water. Widespread poor land use practices contribute to high turbidity in river water, making turbidity management or removal critical, particularly before the water is used for drinking or subjected to chemical treatment. In this study, mucilage from DE was extracted with deionized water and different chloride solutions. A coagulation efficiency of 99% using modified mucilage coagulant was achieved. The modified mucilage of potassium crude extract and sodium crude extract displayed higher coagulation efficiencies than unmodified mucilage of deionized water crude extract. An increase in coagulant dosage and initial turbidity influenced the coagulation efficiency of DE coagulant. A large reduction in turbidity levels of the treated water samples resulted in an improvement in water quality.Keywords: coagulation, Dicerocaryum eriocarpum plant, mucilage, optimise, turbidit

Selective removal of chromium (VI) from sulphates and other metal anions using an ion-imprinted polymer

A linear copolymer was prepared from 4-vinylpyridine and styrene. An ion-imprinted polymer (IIP) specific for Cr (VI) adsorption was prepared by copolymerisation of the quaternised linear copolymer (quaternised with 1,4-chlorobutane), 2-vinylpyridine functional monomer and ethylene glycol dimethacrylate (EGDMA), as the cross-linking monomer, in the presence of 1,1’-azobis(cyclohexanecarbonitrile) as initiator. Ammonium dichromate and aqueous methanol were used as a template and porogenic solvent, respectively. Leaching of the chromate template from the polymer particles was achieved with successive stirring of the ion-imprinted polymer (IIP) particles in 4 M HNO3 solutions to obtain leached materials, which were then used for selective rebinding of Cr (VI) ions from aqueous solutions. Similarly, the non-imprinted polymer/ control polymer (NIP/CP) material was also prepared under exactly the same conditions as the IIP but without the chromate anion template. Various parameters, such as solution pH, initial concentration, aqueous phase volume, sorbent dosage, contact time and leaching solution volumes, were investigated. Scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, BET surface area and pore size analysis were used for the characterisation of IIP (both unleached and leached) and CP materials. Optimal parameters were as follows: solution pH, 3; contact time, 120 min; eluent, 20 mℓ of 0.1 M NaOH; and sorbent amount, 125 mg. Maximum retention capacity of IIP and CP was 37.58 and 25.44 mg∙g-1, respectively. The extraction efficiencies of the IIP and CP were compared using a batch and SPE mode of extraction. In the absence of high concentrations of ions, especially sulphate ions, both CP and IIP demonstrated no differences in binding of Cr (VI), which was almost 100%. However, in the presence of high concentrations of sulphate ions, the selectivity on the CP completely collapsed. The study clearly demonstrates the suitably of the developed IIP for selective extraction of Cr (VI) in complex samples such as those from acid mine drainage. The selectivity was also compared by direct injection of the real-world sample, both spiked and non-spiked, into that obtained after IIP selective extraction. Despite the method’s very low detection limits for direct injection (below 1 μg∙ℓ-1), no Cr (VI) was obtained. However, after IIP selective extraction, spiked Cr (VI) was detected in the spiked sample

Development and validation of a single HPLC method for the determination of thirteen pharmaceuticals in bulk and tablet dosage form

The aim of this study was to develop and validate a high performance liquid chromatography (HPLC) method for the determination of thirteen selected pharmaceutical compounds (metformin, amoxicillin, chloroquine, theophylline, trimethoprim, caffeine, norfloxacin, ciprofloxacin, acetylsalicylic acid, doxycycline hyclate, metronidazole, albendazole and cloxacillin) in bulk and tablet dosage form. Chromatographic separation using a Kromasil C18 column, gradient elution with aqueous formic acid (0.1%), methanol and acetonitrile, a UV absorption wavelength of 250 nm and a mobile phase flow rate of 1 mL/min over a 22 min run time was optimized for complete separation of the selected target compounds. The method was validated and results for: linearity, precision, sensitivity, accuracy, specificity, suitability and method robustness were obtained and met the ICH guidelines. Calibration curve correlation coefficients ranged from 0.9985-0.9998 and the percentage relative standard deviations for repeated analysis was below 5%, indicating acceptable method precision. The limits of detection (LODs) and quantification (LOQs) ranged from 0.020-0.27 µg/L and 0.080-0.91 µg/L, respectively. The accuracy study yielded recoveries in the ranges 86.0-102% for pure compounds and 90.9-106% for compounds in tablet dosage form. The method is robust for small or deliberate changes to the chromatographic parameters and found to be appropriate for analysis of tablets for the determination of the thirteen pharmaceuticals.                     KEY WORDS: Pharmaceuticals, Bulk determination, Tablet dosage, High performance liquid chromatography, Method development, ICH guidelines   Bull. Chem. Soc. Ethiop. 2021, 35(1), 17-31. DOI: https://dx.doi.org/10.4314/bcse.v35i1.

Development and Application of Solid Phase Extraction Method for Polycyclic Aromatic Hydrocarbons in Water Samples in Johannesburg Area, South Africa

A solid phase extraction (SPE) technique has been developed for the quantitative determination of polyaromatic hydrocarbons (PAHs) in aqueous samples. The SPE technique involved extraction of PAHs froma 100 mL sample containing 10 % methanol as a modifier onto C18 cartridges. 40 % methanol in water was used as conditioning solvent, and 3 mL acetone:THF (1:1) as eluting solvent. After eluting, the extract was reduced to 1 mL under nitrogen and then analyzed by GC-MS. The extraction was optimized for the addition of organic modifier, sample load volume, conditioning solvent, washing solvent and eluting solvent. In order to evaluate the practical applicability of SPE technique, water samples were spiked with the PAHs to give final sample concentrationsbetween 3 and 7 μg L–1. Enrichment factors of 81–135 were achieved with relative standard deviations (RSDs) of less than 6 %. Recoveries obtained ranged from 81 to 135 %. Detection limits ranged from 20.0–52.0 ng L–1. The optimized method was validated by analyzing certified reference materials. The optimized method was then applied to spiked real river samples in and around the Johannesburg area, South Africa. The concentrations obtained varied from 22.0 to 1040.0 ng L–1. The RSDs were between 2.3 and 13 %. The overall order of PAHs levels was: phenanthrene > acenaphthene > naphthalene > fluoranthene > pyrene.Keywords: Solid phase extraction, polycyclic aromatic hydrocarbons, water samples, Johannesburg, South Afric