A lack of natural water resources and an increase in the demand for fresh potable water has shifted focus to the possible reuse of recycled laundry wastewater water that is considered to be relatively clean. Organic components such as linear alkylbenzene sulfonates (LAS) are the major and most abundant contributing anionic surfactant constituents found in laundry detergents. The development and reliability of treatment methods targeted at purification of laundry wastewater necessitates a fast and accurate method for quantification of LAS. This paper focuses on a comparative study for the quantification of LAS based on traditional liquid–liquid extraction (LLE) and HPLC–UV methods. In the case of LLE, the anionic surfactant LAS complexes via ion association to a methylene blue (MB) cationic dye resulting in the formation of an anionic surfactant–methylene blue (AS–MB) complex. The AS–MB complex extracted with chloroform absorbs at a λ max of 653 nm. Optimized conditions for quantification of a single eluted LAS peak using HPLC–UV were obtained by isocratic elution on a C18 column with a 95 % acetonitrile and 5 % 0.7 M acetic acid mobile phase. Both methods displayed percentage recoveries >90 % and statistically showed reproducibility and precision in the quantitation of LAS. HPLC–UV prevailed over UV–Vis as the method of choice for LAS determinations given the ease of sample preparation and applicability to a wider range of samples. Typical levels of LAS in laundry samples assessed in this study ranged between 116 and 454 mg L−1.

In this work, experimental and modelling investigations were conducted on biochars pyrolyzed at 350°C and 600°C, to determine the effect of pyrolysis temperature, hydrogen peroxide activation and pH on copper and zinc removal, in comparison with commercially available activated carbons. Characterization of biochars was performed by BET surface area, elemental analysis and FTIR spectroscopy. Experiments results demonstrated that biochar pyrolyzed at 600°C adsorbed both copper and zinc more efficiently than biochar pyrolyzed at 350°C. Chemical activation by H2O2 increased the removal capacity of biochar pyrolyzed at 350°C. All investigated biochars showed a stronger affinity for copper retention, with a maximum adsorption capacity of 15.7 mg/g while zinc was 10.4 mg/g. The best adsorption performances were obtained at pH 5 and 6. Langmuir adsorption isotherm described copper adsorption process satisfactorily, while zinc adsorption was better described by Freundlich isotherm.

Background: Only limited information is available on the disposal methods for spectacle frames, and their interaction with the environment once such disposal occurs.Aim: This study investigates the disposal of spectacle frames and provides a preliminary report on their biodegradability and biocompatibility.Setting: The study was conducted at a university in the south eastern part of South Africa.Methods: The study was conducted in two parts: Part A consisted of an explorative, quantitative design using a closed-ended questionnaire investigating the current disposal methods of 375 spectacle wearers for their old spectacles; and Part B consisted of a descriptive, cross-sectional design involving chemical analyses of metal and plastic spectacle frames.Results: Almost 55% of the participants reported either keeping or reusing their spectacles. Only 5% had used a recycling method when disposing their previous spectacles. Inductively coupled plasma optical emission spectroscopy results showed that metal frames do not degrade easily unless they are oxidised in an acidic environment. Lead was detected in two metal frames. Results of thermogravimetric analysis revealed that plastic frames only begin to degrade at temperatures over 250 °C. Gas chromatography-mass spectrometry results suggest that plastic frames, except three dimensional (3-D) polarisers, are biocompatible as they are stable, not chlorinated and do not possess heavy metals. The results suggested that eco-friendly frames may be the most biocompatible.Conclusion: It appears that few spectacle wearers use recycling for disposing their frames. Current metal and plastic spectacle frames appear to have poor biodegradability but good biocompatibility.

Cross polarisation/magic angle spinning 13 C NMR spectroscopy has been used to study structural changes in cellulose induced by the dissolving pulp process. The cellulose structure in several dissolving pulps was investigated for commercial and laboratory cooked Eucalyptus 92a and 96a. The average lateral dimension, or average thickness, of the cellulose fibril aggregates is related to the amount of surface area exposed and could be one controlling factor for the chemical reactivity of commercial dissolving pulps during modification reactions. The thickness of the cellulose fibril aggregates governs the amount of surface area present in the fibre wall, and cellulose surface material constitutes the part of the cellulose that is directly accessible to reagents. In all sample series investigated, the raw pulp was found to be less aggregated than the corresponding bleached final pulp. Furthermore, an irreversible increase in fibril aggregate width was observed on free drying for both laboratory cooked and commercial pulps. Upon rewetting with water, the freely dried 96a pulp was found to be more aggregated than the freely dried 92a pulp, although sugar analysis showed very similar carbohydrate compositions. As indicated by the molecular mass distribution, the commercial 92a pulp contained larger amounts of degraded cellulose; this may be a plausible explanation for the different behaviour of the 92a and 96a pulps during free drying.

Tuberculosis (TB) accounts for millions of deaths worldwide every year. Diverse survival strategies adopted by Mycobacterium tuberculosis (Mtb) have substantially hindered the existing anti-TB regimen thereby leading to multidrug-resistant (MDR) and extremely drug-resistant (XDR) strains of TB. The steady decrease in current antibiotics' efficacy against these adversities is an indicator that their adequate replenishment in future is almost impossible, placing society on the precipice of a catastrophe. Over the past many years, researchers have been continuously generating new armamentarium of anti- TB drugs by tailoring the properties of available drugs or designing completely new agents. One of these emerging and successful synthetic techniques is molecular hybridization (MH) that involves the integration of different pharmacophoric subunits to form a new prototype with the ability to be recognized by multiple receptors. In most cases, the resultant conjugates have been reported to exhibit superior biological activity profiles relative to their parent molecules which is attributed to their different or dual modes of action. Accordingly, several new effective anti-TB scaffolds have been synthesized using this approach, and are well cited in literature. In this review, we provide a summarized account of the chemical strategies optimistically focused to develop new molecular assemblies for TB via MH approaches. Additionally, the structure activity relationships revealed from different biological assays is systematically discussed.