Functionalization of a Natural Biopolymer with Aliphatic Polyamines and its Sorption Properties for Vanadium Removal from Aqueous Solutions

A low-cost natural adsorbent, Moringa oleifera, was investigated as a potential alternative for currently costly methods of removing vanadium from contaminated aqueous solutions. The unmodified bark was characterized using techniques such as N2-BET, SEM, XRD and FTIR spectroscopy, CHNS elemental determination and AA spectroscopy. Results showed a relatively small surface area, motivating surface functionalization to enhance adsorption capacity. Chemical modification was performed using four aliphatic polyamines: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA). The modified bark was characterized and then investigated to determine its efficiency in removing VO2+ from aqueous solutions. The bark had a mesoporous amorphous structure and was enriched with N and S groups. FTIR absorption frequencies also revealed that polyamines were indeed immobilized on the adsorbent surface. The polyamine density was calculated and was in the order of EDA>DETA>TETA>TEPA, whereas the adsorption efficiency with VO2+ was in the order DETA>EDA>TETA>TEPA. Adsorbent amination was enhanced by up to 26 % and adsorption performance improved by up to 155 %. It was, therefore, concluded that chemical modification of M. oleifera using polyamines enhances adsorption of VO2+ from aqueous solutions. This can, thus, preconcentrate VO2+ in the bark leading to its use as a good water purifier.Keywords: Adsorption, functionalization, Moringa oleifera, polyamine, vanadiu

Impact of Metals on Secondary Metabolites Production and Plant Morphology in Vetiver Grass (Chrysopogon zizanioides)

The impact of selected metals on the production of phenolic compounds was investigated in a pot trial experiment. One-month old vetiver grass (Chrysopogon zizanioides) seedlings were exposed to different concentrations (0, 10, 50, 100, and 500 ppm) of As, Cr, Cu, Fe, Ni, Pb and Zn. All the plants except for those treated with As tolerated up to 500 ppm as they did not show any signs of stress such as wilting or necrosis. A significant decrease (>35 %) in the length of the plants treated with As, compared to the control, was observed at 50 ppm which further decreased with increasing As concentration. A serious case of phytotoxicity was observed at 500 ppm As as the plant could not survive. Total soluble phenolics content in vetiver plants increased with increasing concentration of metals in the growth medium. The amount of the cell wall-bound phenolics (2.01 to 5.84 mg GAE g–1 DW) was higher than the total soluble phenolics (1.13 to 2.14 mg GAE g–1 dry weight DW) and both increased with increasing metal concentrations. Morphological changes associated with metal-induced stress were also examined with a scanning electron microscope which revealed thickened cell walls, loss of cell shape, reduction of intercellular space and the closure of stomata in leaves of metal-exposed plants.Keywords: Vetiver grass, toxic metals, phytotoxicity, phenolic compounds, morphological change

Internal Standard Method for the Determination of Au and some Platinum Group Metals Using Inductively Coupled Plasma Optical Emission Spectrometry

A method is described for the determination of Au, Pt, Pd, Ru and Rh in a converter matte sample, using inductively coupled plasma optical emission spectrometry (ICP-OES), with Y or Sc as internal standard. The results obtained by this method are discussed and compared with values obtained by an independent laboratory. The efficiency of internal standardization was evaluated by varying the operating conditions of the ICP-OES. Changes in the amount of energy transferred from the plasma to analyte, the amount of aerosol reaching the plasma and analyte residence time, were studied in terms of their effect on the emission intensity of the analyte and the internal standard. It was found that changes in the emission signals of the PGMs due to power variations could be effectively compensated for, using either Sc, Y or Ar lines as internal standards. For variations in aerosol gas flow rate, both Sc and Y could only compensate for Pd and Au between flow rates of 0.60 and 0.80 l min -1 and for Pt, Ru and Rh at 0.80 l min -1. The effect of sodium on the determination of Au and the PGMs, and the use of Sc and Y as internal standards, to compensate for Na matrix effects on accuracy were also studied. It was found that emission intensities of the analytes decreased with increasing Na concentration. Furthermore, Sc as an internal standard could compensate for Pt, Ru and Rh up to 5 g l-1 Na, while Y could only compensate for the same elements up to 1 g l -1 Na. South African Journal of Chemistry Vol.55 2002: 72-8

SODIUM REDUCTION IN PROCESSED FOODS, INCLUDING PROCESSED MEATS, IN AFRICA: A SYSTEMIC REVIEW

The use of sodium in processed foods, including meats, has been in existent over centuries. Its use is mainly as a food and meat processing aid, and a preservative and flavourant. Even with modern methods of food processing, sodium is still essential in food and meat derivatives due to different dietary demands by consumers. Sodium chloride, sodium nitrate and nitrite are common in meat processing for various uses such as curing, smoking and brining. Due to the increasing global sodium intake, chronic adverse health effects, such as cardiovascular diseases, hypertension, stroke, cancers, among others, have also been on the rise, particularly in urban areas. African countries have a proportional increase of dietary sodium due to the adoption of western diets with high sodium and saturated fats. Subsequently, South Africa promulgated legislation that prescribed the first mandatory sodium limits in 2013. The purpose of this review is to determine, (1) the sodium reduction interventions agreed by African states in forums and meetings in the past five years (2017-2021) and, (2) sodium reduction strategies recommended through research by African scholars. This systemic review was conducted from English literature published between 2017 and 2021, using Science web, MEDLINE, CINAHL, PsycINFO, Science Direct, PubMed, Google Scholar, with a specific focus on African countries. From the findings of this systemic review, there were minimal sodium reduction interventions by African states, emanating from published forums and meetings, to establish collaborated sodium reduction strategies in processed foods. The studies conducted by African scholars in the past five years recommended sodium reduction interventions, such as legislative framework, product reformulation, monitoring models and consumer awareness, with most studies done in South Africa. It is evident that to have a meaningful impact on the control and reduction of dietary sodium, African countries require existing diplomacies to collaborate on sodium reduction efforts with public and private partnerships; this can be coordinated through inter-trade treaties among the African states. This requires an increase in research, commitment and the will to reduce dietary sodium in processed foods and meat by all member states

SODIUM REDUCTION IN PROCESSED FOODS, INCLUDING PROCESSED MEATS, IN AFRICA: A SYSTEMIC REVIEW

The use of sodium in processed foods, including meats, has been in existent over centuries. Its use is mainly as a food and meat processing aid, and a preservative and flavourant. Even with modern methods of food processing, sodium is still essential in food and meat derivatives due to different dietary demands by consumers. Sodium chloride, sodium nitrate and nitrite are common in meat processing for various uses such as curing, smoking and brining. Due to the increasing global sodium intake, chronic adverse health effects, such as cardiovascular diseases, hypertension, stroke, cancers, among others, have also been on the rise, particularly in urban areas. African countries have a proportional increase of dietary sodium due to the adoption of western diets with high sodium and saturated fats. Subsequently, South Africa promulgated legislation that prescribed the first mandatory sodium limits in 2013. The purpose of this review is to determine, (1) the sodium reduction interventions agreed by African states in forums and meetings in the past five years (2017-2021) and, (2) sodium reduction strategies recommended through research by African scholars. This systemic review was conducted from English literature published between 2017 and 2021, using Science web, MEDLINE, CINAHL, PsycINFO, Science Direct, PubMed, Google Scholar, with a specific focus on African countries. From the findings of this systemic review, there were minimal sodium reduction interventions by African states, emanating from published forums and meetings, to establish collaborated sodium reduction strategies in processed foods. The studies conducted by African scholars in the past five years recommended sodium reduction interventions, such as legislative framework, product reformulation, monitoring models and consumer awareness, with most studies done in South Africa. It is evident that to have a meaningful impact on the control and reduction of dietary sodium, African countries require existing diplomacies to collaborate on sodium reduction efforts with public and private partnerships; this can be coordinated through inter-trade treaties among the African states. This requires an increase in research, commitment and the will to reduce dietary sodium in processed foods and meat by all member states