A mini‑review of the morphological properties of biosorbents derived from plant leaves

摘要

A key feature of biosorption studies is the utilisation of different analytical techniques to evaluate several aspects of the process. Scanning electron microscopy (SEM) is used to study the morphology features of biosorbents. In this mini-review, research efforts by scientists in evaluating the morphological properties of plant leaves biosorbents was discussed. The way in which results have been interpreted and what inferences have been deduced was also discussed. Biosorbents obtained from plant leaves generally possess heterogeneous and irregular surface containing a variety of cavities, holes, voids, cracks, interstices and convolutions. NaOH pre-treatment (also known as mercerisation) helps to remove lignin and oil from the biomass as well as increasing the roughness of the base cellulose. Smoother surfaces with fewer features are observed after sorption of some chemical species (be it pollutants or a modification agent). It was observed that impregnation with nanoparticles usually leads to nanoparticle macro-clusters observable at high resolutions while any previously observed cavities, holes, ruptures and voids tends to disappear. Carbonisation and calcination gives a more porous adsorbent. Chemical modification despite reducing the total surface area of the adsorbent can actually increase the adsorption capacity due to adjustments in functional groups, effects on the solution chemistry and the improvement of the inherent affinity of the biosorbent due to the modification. SEM analysis is even more important in recent times where the functionalisation of adsorbents and biosorbents is a common practice.