Sustainable phosphorylated microcrystalline cellulose toward enhanced removal performance of methylene blue.

In this study, microcrystalline cellulose (MCC) was phosphorylated using phosphoric acid in the presence of urea and used as an adsorbent for methylene blue (MB) dye removal from an aqueous solution. The obtained products were characterized by different techniques. Batch adsorption experiments were conducted under varying conditions of incubation time, initial MB concentration, pH, and phosphorylation degree. All the samples exhibited similar and fast adsorption kinetics, described by pseudo-second-order model for MB adsorption, whereas the retention capacity depended significantly on the phosphate content and the surface charge of the adsorbents. The experimental adsorption data in the examined MB initial concentrations (0-2000 mg/L) were best suited by the Langmuir isotherm model. The study revealed that the presence of phosphates groups in the cellulose structure significantly enhanced the adsorption of the MB pollutant. The maximum dye removal capacity at pH of 7 was obtained for the phosphorylated microcrystalline cellulose (284.03 mg/g) with a high phosphorylation degree (1.92 % of P), which is 20 times higher than unmodified MCC (15.29 mg/g). This property increased from 284.03 to 328.32 mg/g when increasing the pH from 7 to 11. The MB adsorption mechanism involves hydrogen bonding, electrostatic and ion-dipole interactions. These findings are relevant to a better understanding of the role of cellulose phosphorylation in the recovery of organic dyes from the waste liquid of many industries.

A review on the demineralisation of pre- and post-pyrolysis biomass and tyre wastes.

Pyrolysis is an attractive technology to convert low-cost carbonaceous waste materials into fuels, energy and other value added products goods. During pyrolysis, the inorganic minerals present in the feedstock can cause problems to the equipment and give side reactions. Besides, the minerals present in the chars can hinder their possible applications. Therefore, it seems necessary to eliminate said contaminants in order to valorise the aforementioned goods. Demineralisation is a process widely used for purifying materials that are contaminated with inorganic matter. Although this technique is commonly used with waste materials that will undergo pyrolysis, or the products obtained from it, the studies analysing this practise are rather scattered. The aim of this paper was to compile and review the current literature concerning the demineralisation of carbonaceous waste (tyres and lignocellulosic biomass) materials. The chemistry involved, feedstock type and the effect of performing the purifying step before or after pyrolysis were addressed in this work. The review revealed that biomass samples should be demineralised before pyrolysis in order to affect not only the char but also the bio-oil quality. Depending on the form in which the minerals are linked to the structure, the solvent chosen will vary (from water to strong acids). However, water is the most popular option due to its price and easy disposal. In tyres, demineralisation should be performed after pyrolysis using strong acid and subsequently base. Due to the crosslinked chemical structure, rubber is highly resistant to chemicals thus the pre-treatment has to be avoided.