M.Sc Thesis

M.Sc StudentGilelah Alexander
SubjectCharacterization of Plant Cell Walls as Filtration and
Sorption Media for Toxic Gases and Fine Aerosols
DepartmentDepartment of Civil and Environmental Engineering
Supervisors PROFESSOR EMERITUS Peter Neumann


The aim of this research was to characterize plant cell walls as a sorption and filtration media for ammonia, hydrogen sulfide, propyl acetate (representing hazardous organic compounds) and micron size particles, by comparison with activated carbon. Filtration media consisting of cell wall powder were derived by hot ethanol extraction, filtration and drying of finely ground plant tissues. Adsorption capacities of cell wall filtration media prepared from primary or secondary walls from different tissues of monocot or dicot plants were determined. The influences of different physical factors, such as compaction, flow rate, path length, surface area and humidity on the adsorption and filtration capacity of the media were studied. In addition, adsorption capacities of the major cell wall components (i.e. cellulose, pectin, protein and lignin) were determined. The influence of chemical modifiers such as weak acids or strong oxidizers on the adsorption capacity of cell walls and activated carbon was also investigated. Secondary cell wall material prepared from dicot pine wood absorbed ammonia with about 60% the efficiency of activated carbon and with near equivalent  efficiency after chemical modification with citric acid. Other plant sources of primary or monocot cell walls proved less effective than pine wood. The best results were obtained for higher densities of filtration media and lower rates of ammonia injection through the filter. All of the polymer components of cell walls were capable of some ammonia absorption but the most active component was pectin. The hydrogen sulfide adsorption capacity of all the studied types of cell walls was low, as was the adsorption capacity of activated carbon for this gas. Adsorption of propyl acetate vapor by cell wall media was very low as compared with activated carbon. Chemical modifications did not improve the adsorption of propyl acetate. Cell wall powder was able to completely remove microparticles of smoke, ranging from 0.2  to  0.8 ┬Ám diameter, from an air stream during a 3 h assay. Cell wall powder therefore showed promise as a microparticle air filter, certainly in comparison with activated carbon and cellulose powder. Moreover, the cell wall powder reduced particle concentrations in air with a relatively low pressure drop compared to the other materials studied.