Characteristics and mechanisms of sustainable recovery of perlite from carrageenan residue by green technology and its application in carrageenan extraction

A large amount of carrageenan residue containing perlite is produced in carrageenan process. Management of carrageenan residue is an environmental issue in carrageenan green and clean production. Repeated recovery of perlite from carrageenan residue could reduce resource waste and environmental pollution. However, research on methods, reuse characteristics, and mechanisms of repeatedly recovered perlite remains lacking. In this study, a green recovery scheme was obtained to recover perlite by combining food-grade hydrochloric acid and hydrogen peroxide, and influence of elemental structure changes on gel structure during repeated recovery was investigated. The permeability of recovered perlite (2.61/Darcy) reached reuse standard, showing good economic value. The C–O–C bond of polysaccharide and inner ether galactose ring in carrageenan residue were degraded by hydrogen peroxide and hydrochloric acid. More importantly, gel strength and transparency of carrageenan increased by 42.86% and 16.46% with recycling times, probably due to repeated adsorption and release of K+ from recovered perlite. The C–K bond effectively shielded electrostatic repulsion between carrageenan segments and promotes formation of gel network. The characteristics of carrageenan and recycling times were consistent with gaussian model, y=y0+Awπ/2e−2(x−xc)2w2, with a maximum number of cycles of 4.21. It provides a technical research basis for green and clean carrageenan extraction.