Surface and adsorptive properties of Moringa oleifera bark for removal of V(V) from aqueous solutions Robert Londi Mnisi & Peter Papoh Ndibewu Received: 2 September 2016 /Accepted: 26 October 2017 # Springer International Publishing AG, part of Springer Nature 2017 Abstract The bark of Moringa oleifera, a cheap and readily available natural biopolymeric resource material, found to significantly reduce coliform load and turbidity in contaminated water is investigated in this paper. Its surface and adsorptive properties are investigated to explore its adsorptive potential in removing V(V) from aqueous solutions. Surface properties were investigated using FTIR, HRSEM/EDS, IC, and BET-N 2 adsorption techniques. Adsorptive properties were investigated by optimizing adsorption parameters such as pH, tempera- ture, initial metal concentration, and adsorbent dosage, using V(V) as an adsorbate. The adsorption-desorption isotherms are typical of type II with a H3 hysteresis loop and is characteristic of a largely macroporous material. Bottle ink pores are observed, which can provide good accessibility of the active sites, even though the internal BET surface area is typically low (1.79 g/m 2 ). Solution pH significantly influences the adsorptive potential of the material. The low surface area negatively impacts on the adsorption capacity, but is compensated for by the exchangeable anions (Cl - ,F - , PO 4 3- , NO 3 - , and SO 4 2- ) and cations (Ca 2+ ,K + , Mg 2+ , and Al 3+ ) at the surface and the accessibility of the active sites. Adsorption isotherm modeling show that the surface is largely het- erogeneous with complex multiple sites and adsorption is not limited to monolayer. Keywords Moringa oleifera . N 2 -BET adsorption . Surface area . Isotherms . Surface pores Introduction Understanding surface properties of adsorbents for pol- lutant removal is critical in their design, optimization, and application. A wide range of synthetic, natural, and chemically modified biopolymeric adsorbents have been proposed and applied for different pollutant types with different degrees of success (Zeng et al. 2011). The use of natural biopolymeric adsorbents has received much attention lately, in promotion of green chemistry principles. Most of these materials are non-competitive agricultural by-products; thereby rendering them readily available, at low cost and, depending on their surface properties, require minimum chemical modification. A readily available biopolymeric material, Moringa oleifera, has been found to significantly reduce coliform load, is an effective coagulant (Alo et al. 2012), removes turbidity (Okuda et al. 2000), and can also significantly remove color (Prasad 2009) from contaminated water. These research findings are based on analysis of the leaves and seeds of M. oleifera, and not much is reported on the use of the bark or wood, which are often discarded as firewood. This renders the bark as a non- competitive, cheap, and readily available agricultural resource which can be explored for other uses. Hence, this investigation applies different characterization Environ Monit Assess (2017) 189:606 https://doi.org/10.1007/s10661-017-6329-0 R. L. Mnisi (*) : P. P. Ndibewu Department of Chemistry, Tshwane University of Technology, Private bag X680, Pretoria 0001, South Africa e-mail: mnisirl@tut.ac.za