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Graphical abstract Highlights • The adsorbent has a highly ordered, multilayer-like composite structure. • The sorption process followed the pseudo-second-order kinetic model. • Adsorption of Cd2+, Ni2+ and Cr3+ ions onto the surface of OPC was heterogeneous. • Thermodynamic studies suggested physical adsorption for the removal of, Pb2+. • Physico-chemical process may be involved in the adsorption of Cd2+, Ni2+ and Cr3+. Abstract The efficiency of oil palm calyxes (OPC) in removing heavy metals from aqueous solution is presented in this report. Qualitative analyses showed the participation of hydroxyl, carboxylate and methoxyl groups in the binding process. OPC surface was observed to be amorphous, highly ordered and multilayered. Quantitative analyses indicated that the removal of Cd2+, Pb2+ and Ni2+ occurred at fast kinetics, with uptake of 38.24, 47.66 and 32.61 mg/g respectively, after 5 min. Optimum Cr3+ adsorption was however not reached after 3 h, indicating slow kinetics. Pseudo-second-order model best described the kinetics of the adsorption, suggesting chemisorption as the rate-limiting step. Metal uptake increased with rise in adsorbate concentration. However, no further rise in uptake was observed with increase in Pb2+ concentration beyond 200 mg/L. Data from the sorption of Cd2+, Ni2+ and Cr3+ were best described by Freundlich isotherm, while those of Pb2+ obeyed Langmuir isotherm, with maximum adsorption capacity (q max) of 120.48 mg/g. Thermodynamic studies indicated that the removal of Cd2+, Ni2+ and Cr3+ was exothermic and occurred with decreased disorderliness, while Pb2+ removal was endothermic with increased entropy. The negative values of ΔG° indicated the spontaneity of the biosorption of Cd2+, Pb2+, Ni2+ and Cr3+ onto OPC. [ABSTRACT FROM AUTHOR]

Abstract: Starch was isolated from unripe plantain fruit and it was chemically modified where it was hydroxypropylated to improve upon the functional properties of native plantain starch. The yield of the starch was ∼19% and molar substitution increased with increase in concentration of propylene oxide. ‘C’ type X-ray diffraction was shown by native plantain starch and many changes were not noticed after hydroxypropylation. The granules were oval or elliptical in shape with 10–20μm in width and 15–40μm in length, modification did not bring about major changes in size and shape except partial erosion of the granules. Hydroxypropylation also improved the swelling capacity from ∼20 in native to 90g/g. Turbidity reduced after hydroxypropylation and increase in molar substitution. Syneresis reduced by 75% with increase in MS. Thermal studies by DSC revealed that all the parameters decreased after this modification. Onset temperature reduced by ∼26%, peak temperature reduced by ∼9%, endset temperature increased by ∼6%, gelatinization temperature range increased by 137%, enthalpy decreased by 38%. Reduction in all parameters were noticed during 3rd and 18th day scan. Enthalpy of retrogradation as well as percentage of retrogradation reduced to a greater extent during the 3rd as well as the 18th day scanning. [Copyright &y& Elsevier]