Water hyacinth biochar and Aspergillus niger biomass amalgamation potential in removal of pollutants from polluted lake water

Abstract The excess load of organic and inorganic pollutants in Chanramkudi Lake water creates eutrophication resulting from excess growth and spreading of water hyacinth and bad odour and provides favourable circumstances for the survival of disease spreading insect vectors and possibilities of disease occurrence. The results showed that the suitable temperature and residence time for the conversion of dried biomass of water hyacinth into useful biochar was 350 °C and 60 min, respectively, and 33.6% of water hyacinth biochar (WHBC) at stable organic content basis of 49.2% was produced. The WHBC produced under this condition had physicochemical properties such as 389.8 mmol kg-1 of CEC (Cation Exchange Capacity), 69.1 of C/N, 68.2 of C, 234.7 mg kg-1 of total P, 19.7% of ash, and 59.4% of volatiles with pH 7.9. The metal adsorbing competence of this WHBC with and without A. niger was tested with various concentrations (250, 500, 750, and 1000 mg L-1) of various metal (Cd, Cr, and Pb) containing solutions. The WHBC with A. niger amalgamation (15:3 g) effectively adsorbed the metals even at 1000 mg L-1 such as Cr (91.5%), Cd (95.6%), and Pb (93.9%) than individually. The metals were adsorbed and immobilized in the pores of WHBC and the outer layer of the cell wall of A. niger was observed under SEM analysis with various scaling (50, 100, & 150 µm). Further, the pollutant adsorbing functional groups were found in both WHBC and dead mycelia biomass of A. niger through FTIR analysis. The attained results concluded that the biochar produced from challenging water hyacinth could adsorb and minimize the pollutants with an amalgamation of A. niger. Significantly, more volume (33.6%) of biochar can be derived from water hyacinth. Furthermore, WHBC and A. niger are easily cultivable. Thus, it could be preferably useful for removing real-world organic and inorganic pollutants from polluted water.