This work was carried out in collaboration between all authors. Author VIO designed the study and wrote the protocol. Author LOA performed the sampling and managed the analyses of the study. Author MNM managed the literature searches and wrote the first draft of the manuscript. All authors read and approved the final manuscript.

Groundnut shell, an agricultural waste was used as a precursor for the preparation of activated charcoal using zinc chloride as a chemical activating agent. The results of the optimization studies showed that the activated charcoal had best iodine adsorption capacity at 1.0 mol dm-3 activator’s concentration, 2:1 impregnation ratio, 70 ℃ impregnation temperature, 12 hr impregnation time, 500 ℃ activation temperature, and 2hr activationtime. The surface chemistry of the adsorbent was studied by Fourier transform infra-red spectroscopy and scanning electron microscopy–energy dispersive X-ray spectroscopy. The activated charcoal was found to contain porous structures with adsorption capacities significantly correlated with iodine value, porosity, and surface area. The surface morphology of the activated charcoal was altered as compared with the un-activated product, signifying that the adsorbent had been chemically modified. The disappearance of some functional groups and shift in some absorption bands were further indication that surface structural modification took place during activation and carbonization.This research has revealed that groundnut shell could be employed for the production of an alternative adsorbent which can be utilize for filtration and detoxification of impure water, treatment of effluent and wastewater, adsorption of pesticides, heavy metals and dyes from aqueous media.

This work was a realization of collaboration between all authors. Author EOO wrote the protocol and the first draft of the manuscript. Author LOA designed the study, performed sample and data collection, and provided statistical expertise. Author AGF managed the literature searches and manuscript preparation and analyzed the study. All authors were actively involved in experimental processes, read and approved the final manuscript.

No abstract

Purpose Leafy vegetables are known to be highly perishable because of high moisture content, which had resulted in applications of different preservative methods. However, these methods were not without certain limitations during storage. Osmotic pre-dehydration had been proved to be a better alternative because of high retention and improvement in nutritional qualities and stability during storage. This study aims to investigate the osmotic pre-dehydration of fluted pumpkin (Telfairia occidentalis) leaves. Design/methodology/approach Fluted pumpkin (T. occidentalis) leaves were pre-dried using sucrose, corn syrup and sodium chloride solutions as osmotic agents, while unosmo-predried leaves were used as the control. Both osmo-predehydrated and unosmo-predried leaves were dried in a hot air oven, whereas the effect of the osmotic agents on the nutritional qualities was investigated using standard protocols. Findings There were significant differences (p-values ranged from 0.001 to 0.030) in the proximate compositions of samples. Osmo-predried leaves recorded higher mineral contents in Ca, Cu, Fe, K, Mg, Mn and Na. Osmotic pre-dehydration by NaCl had a significant effect (p = 0.02) on ascorbic acid. The amino acid profile of the oven-dried leaves (unosmo-predried) showed that histidine and cysteine recorded high amino acid scores of 120.42% and 135%, respectively. Threonine (43.73%) recorded the highest essential amino acid score (without histidine). The economic evaluation indicated the percentage cost index difference of leaves treated with NaCl as 2.08%, sucrose (11.19%) and corn syrup (16.43%). Originality/value The high proportion of beneficial elements such as calcium, magnesium, phosphorus, potassium and appreciable chemical compositions of the osmo-predried leaves compared to unpre-dried leaves proved osmotic pre-dehydration as a value-added technique for preservation of leafy vegetables. The best osmotic agent was sodium chloride. This process could be applied on a small scale for the development of self-entrepreneurs and home-scale industries.