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This study was aimed to investigate the efficiency of locally available low-cost and eco-friendly activated agricultural biosorbents produced from corncob and sorghum husk for the removal of fluoride from aqueous solution using batch adsorption. The activated biosorbents were characterized using SEM, XRD and FTIR spectroscopy. Effects of particle size (0.063–1.0 mm), contact time (15–120 min), pH (2–12), dose (2–10 g), and initial concentration (0.5–5.0 mg/L) were investigated. The morphology analysis revealed that biosorbents showed the presence of a high binding capacity for fluoride adsorption. The maximum adsorption was attained; size of the adsorbent 0.063 mm, pH 7, contact time 60 min, and 6 g dose of the biosorbents. Moreover, the adsorption kinetics followed the pseudo-second-order model and the adsorption isotherms fitted well to the Langmuir model. Furthermore, a field study was conducted using real water sample collected from Semema, Tigray, Ethiopia, and maximum fluoride removal was observed to be 79.44% and 77.05% for the activated carbons of Corncob and Sorghum husk at optimum conditions. Therefore, this experimental finding indicated that activated carbon of Corncob and Sorghum husk can be used as efficient, cheap, and eco-friendly biosorbents for the removal of fluoride from drinking water at community level.

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The purpose of this study was to investigate the toxicological effect of Pb, Cd and Cr in vegetables. Water, soil and vegetables samples were collected to determine heavy metal content using FAAS and its impact on human health via consumption of vegetables. The heavy metals for water samples were recorded in the order of Pb>Cd>Cr, and all, except Cd, were found under WHO/FAO limits. Similarly, the heavy metals of soil samples were also recorded in the order of Cr>Cd>Pb, which was under Ewers and EU permissible limits. On lettuce, mean levels of heavy metals were Pb 0.34 ± 0.04 mg/kg, Cd 1.07 ± 0.12 mg/kg and Cr 3.50 ± 0.23 mg/kg were recorded above the WHO/FAO limits. On onion, levels were 0.75 ± 0.05 mg/kg for Pb, 0.41 ± 0.04 mg/kg for Cd and 1.98 ± 0.27 mg/kg for Cr, which were above the WHO/FAO limits. The high metal content could be attributed to high anthropogenic activities. The TF (transfer factor) for the heavy metal in vegetables also showed a trend of Cd>Pb>Cr. The TF of Cd on lettuce ranged between 0.827 and 0.914, because of the high Cd mobility and its high bio-accumulation factor in lettuce. Thus, TF values of vegetables above 0.5 are considered to be contaminated and thus needs for continuous follow-up. However, the health risk index and daily intake rate of heavy metals of the study indicates the vegetables are safe to eat. But, due to the bioaccumulation nature of the heavy metals and the continual use of these vegetables with increase anthropogenic activities and demand of people for vegetables may pose health problem.