Optimising reaction variables for the preparation of superabsorbent iron fertiliser hydrogel using sugarcane bagasse: A sustainable approach to improve crop nutrient release 

Abstract

Iron (Fe) is a vital micronutrient essential for crop growth and development. Utilisation of bio-based, environmentally friendly functional polymers is inevitable for society. As an alternative to the conventional Fe fertiliser, the present study aimed to synthesise a higher Fe percentage containing hydrogel with organic substances that can facilitate the slow release of nutrients, reduce fertiliser nutrient fixation, and minimise environmental pollution. The reaction variables were optimised for the preparation of superabsorbent using sugarcane bagasse and nano-zeolite-based slow-release Fe fertiliser (SR Fe) hydrogel. This was formulated by graft, co-polymerising acrylic acid, acrylamide, sugarcane bagasse, and nano-zeolite with N,N'-methylene bis-acrylamide as a crosslinker and ammonium persulfate as an initiator. Based on the swelling percentage, the reaction variables of the SR Fe fertiliser were standardised. The crosslinker (MBA - 10 wt%), the initiator (APS - 10 wt%), the filler (Nano-zeolite - 10 wt%), the monomer acrylamide composition (AAm - 2g), the acrylic acid content (AA - 7 ml), the reaction temperature (60oC), and the drying temperature (40oC) were chosen based on desirable swelling percentage and loaded with Fe fertiliser. The Fe fertiliser was loaded to sugarcane bagasse in different ratios (1:0.5, 1:1, 1:1.5, 1:2). The present study showed that the SR Fe fertiliser with the highest percentage of Fe (6.4%) in the ratio of sugarcane bagasse to Fe fertiliser of 1:2 could be used as an effective SR Fe fertiliser to supply nutrients slowly to crops to meet their nutrient needs and improve nutrient use efficiency.