Lead remediation of contaminated water using moringa stenopetala and moringa oleifera seed powder

ABSTRACT

The increasing influx of heavy metals into water bodies from industrial, agricultural, and domestic activities is of global concern because of their well documented negative effects on human and ecosystem health. A recent study of streams in Blantyre and Zomba, Malawi revealed lead levels of up 0.118 mg/L, exceeding the World Health Organisation acceptable level of 0.01 mg/L. Our ongoing study on low cost effective heavy metal remediation techniques in developing countries has already demonstrated that Moringa oleifera, the well known source of natural water clarifiers, is effective in heavy metal detoxification of water. This paper presents the first reported use of a related species, the African moringa, Moringa stenopetala for lead detoxification and preliminary investigation of the interaction of the metal with the polyelectrolytes of M. oleifera and stenopetala. The potential of M. stenopetala for lead removal was tested by means of jar tests. With an initial lead concentration of 7 ppm, M. stenopetala seed powder, at doses of 0.50, 1.00, 1.50, 2.00 and 2.50 g/100mL, reduced the concentration of lead by 20.00 +/- 0.00, 46.19 +/- 2.06, 71.19 +/- 2.06 and 89.43 +/- 0.60 and 96.23 +/- 0.12% respectively. M. stenopetala was more effective than M. oleifera in removing lead from water [p=0.001 at 95% confidence level]. For oleifera, lead levels decreased exponentially during the first 5 h. of the reaction and then equilibrium was established; for stenopetala, a linear decrease was observed. The pH of the mixture rose from 2.30 to a maximum of 2.53 and 2.57 and then fell to an equilibrium value of 2.30 and 2.29 for oleifera and stenopetala respectively. Lead removal was also affected by pH, ionic strength, and water hardness. Our results show that M. stenopetala has potential in lead remediation of contaminated waters. Further studies are being carried out on remediation of other metals and the mechanism of the metal moringa interaction