Converting date seed biomass into highly absorbing hydrogel

Abstract

Converting biomass into value-added products has attracted great attention in recent years. In this paper, a facile approach for using date seed powder without delignification is introduced to convert date seed biomass into a water-absorbing polymer. The biomass of date seed as a source of polysaccharides was immersed in the emulsions of acrylic microgels with different chemical structures. Different polymer latexes based on acrylic acid (AA), sodium acrylate (SA), acrylamide (AM) and 2-acrylamide-2-methyl propane sulfonic acid (AMPS) were prepared using inverse emulsion polymerization. A chemical reaction was carried out between date seed and acrylic latex by heating, which caused the conversion of date seed into a semi-synthetic hydrogel with 60 % natural and 40 % synthetic components. The best modification of date seed to absorbing hydrogel was obtained with poly(AA–SA–AM–AMPS). The modified date seed with this latex had water absorbency of up to 71 g/g, while the unmodified date seed had only 0.2 g/g water absorbency. Date seed hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), rheometric analysis and swelling measurement. The effect of several modifications of parameters such as latex type, AMPS content in latex, aquatic–organic phase ratios of latex and modification temperature on the swelling properties of hydrogel was investigated. The obtained hybrid hydrogel based on date seed biomass contained a considerable amount of biomass in its structure as well as 71 g/g water absorbency, which can be a proper candidate for agricultural applications.