Background

The process of removing negatively charged impurities such as fluoride, nitrate, nitrite, phosphate, sulfate, and other ions from water is necessary in order to effectively make cleaner water. There have been multiple processes and methods implemented to achieve this, however, there hasn’t been an appropriate balance between cost and efficiency. The most efficient processes are often the most costly and require materials that aren’t readily available, whereas the cheapest methods are the least efficient.There is also the issue regarding environmental damage through toxic byproducts and contamination from certain methods of water purification.Therefore a need exists for a process that can separate negatively charged impurities from water without causing significant environmental harm and is also cost‑effective.  

Technology

This technology revolves around organic‑inorganic composite scaffolds that include a negatively charged cellulose substrate (such as regenerated micro fibrillated cellulose, nano‑fibrillated cellulose, cellulose nanocrystals, or cellulose nanofibers) and a high concentration of metal oxide nanocrystals (such as ZnO, FeO, TiO2). In this process, the metal nanocrystals are securely and strongly anchored on the cellulose substrate surface.The cellulose substrate itself can have partially or fully disintegrated cellulose fibers, but depending on whether they are micro fibrillated cellulose fibers or nano‑fibrillated cellulose fibers, the dimensions can vary. For micro fibrillated cellulose fibers the length has to be equal to or greater than 250 nm and the diameter has to be less than or equal to 150 nm. For nano‑fibrillated cellulose fibers, the length has to be greater than or equal to 100 nm, and the diameter has to be less than or equal to 50 nm.The preparation of cellulose substrate includes chemical treatment (regeneration/precipitation), sulfonation, oxidation, combined chemical/mechanical treatment (such as homogenization, micro‑fluidization).From the combination of the metal oxide nanocrystals and the cellulose substrate, the resulting organic‑inorganic composite is a very effective adsorbent for removal of negatively charged impurities from water.

Advantages

The cellulose fibrous substrate is sustainable and very cost‑effective.This composite has higher efficiency as an adsorbent when compared to existing adsorbents.The substrate is also non‑toxic.The purifying agent in this process has multiple uses as it can be substituted as a flocculant, coagulant, filter, membrane, or beads to extract arsenic and other toxic impurities from water. The composite can also be utilized to construct filters that have adsorbent properties.The process is expeditious as it can be done within 5 minutes.There is no secondary contamination.The cellulose substrate and the metal oxides can be recycled at the end of the process. 

Application

This technology is used in the process of purifying water. The composite can extract negatively charged impurities from water, and it can also be expanded to act as a filter, coagulant, or flocculant as well.