Kappa carrageenan-vanillin composite hydrogel for landfill leachate wastewater treatment

Removing heavy metals from landfill leachate wastewater treatment is an environmental challenge because of its complicated characteristics and composition. Although several chemical and physical processes were developed for landfill wastewater treatment, membrane technologies are still common. Nevertheless, membrane fouling, energy requirements and brine management are drawbacks of membrane technologies. This study proposed a biodegradable, gravity-driven kappa-Carrageenan-vanillin hydrogel for biologically treated leachate wastewater treatment to reduce the treatment cost and brine management problem. The composite hydrogel was synthesized using a facile method, with an average pore size of 2.58 ± 0.5 nm and acts as a water filter with super high flux and excellent rejection for heavy metal ions, divalent ions and other contaminants in the landfill leachate wastewater. The hydrogel filter achieved high rejection for divalent ions from salt feed solutions such as sodium chloride, magnesium sulphate, and copper sulphate. An average rejection of 42 ± 5 % was achieved for sodium chloride, 78 % ± 5 % for copper, 72 % ± 5 % for divalent magnesium ion, and 17 % ± 5 % for sulphate rejection. The hydrogel filter achieved a flux of 27 ± 5 LMH for landfill leachate wastewater with high rejection efficiency for total organic carbon, turbidity, and heavy metal separation. The filtration of the landfill leachate with the hydrogel resulted in a high rejection of total organic carbon (77 ± 3 %), 95 ± 3 % turbidity removal, 73 ± 5 % TDS removal, and 95–97 % colour removal. Heavy metal ions were rejected in the following order: Al (80 ± 3 %) > Ba (88 ± 2 %) > Pb (79 ± 3 %) > Cd (72 ± 3 %). The composite hydrogel filter is inexpensive, reliable, and highly efficient in removing contaminants under gravity filtration, requiring no external energy or high hydraulic pressures and ease of scalability for commercial applications.