Application of Rice (Oryza Sativa) Husk as a Sorption Material for the Removal of Pollutants from Aqueous Media (A Review)

Abstract

The applications of rice husk (waste from Oryza sativa production) as a sorption material for the removal of pollutants of various classes, namely, inorganic (Cr, Ni, Co, Pb, Hg, As, Cd, Cu, Zn) and organic (synthetic and natural dyes, phenols, antibiotics, polycyclic aromatic compounds, humic acids, pesticides, chitosan) substances from aqueous media were summarized. Published data on the structure of rice (Oryza sativa) and its acreage, as well as on the chemical composition and some components of rice husk were presented. The methods of physical and chemical (use of inorganic acids, salts, and alkalis) activation, as well as modification of rice husk using surfactants, Fe3O4 nanoparticles, functional agents, and monomers (polymerization reactions) were described. Quantitative characteristics of absorption of various pollutants (removal efficiency, maximum equilibrium sorption capacity) were given. The influence of pH, temperature, pollutant concentration, phase contact time, and rice husk volume and mass on sorption and removal of pollutants from aqueous media was shown. Possible sorption mechanisms, as well as kinetic and sorption models were described. It was revealed that the isotherms of sorption of pollutants in most cases are most adequately described by Langmuir and Freundlich models, and the kinetics of the process, by a pseudo-second-order model.