The　spent　adsorbent　loaded　by　toxic　metals　is　a　solid　hazardous　waste　which　could　cause　significant　secondary　pollution　due　to　potential　possible　additional　release　of　metal　ions.　Therefore,　the　main　subject　is　direct　reutilization　of　spent　adsorbents　which　can　further　economically　and　realistically　offer　new　features,　like　recycling　metal　adsorbed,　or　formation　of　functional　SiO2-based　nanocomposites.　The　nanoporous　structure　and　negative　surface　charges　enable　steel　slag-derived　amorphous　calcium　silicate　hydrate　(CSH)　to　retain　effectively　the　incoming　metal　ions　(e.　g.　Au3+,　Ag+,　Pd2+,　Fe3+,　Co2+,　Ni2+,　Cu2+,　Zn2+,　Ce3+,　Y3+,　and　Gd3+)　by　chemisorption.　Sparked　by　natural　carbonation　‘weathering’,　which　ultimately　sequestrates　atmospheric　CO2　by　alkaline　silicate　minerals　to　leach　calcium　from　mineral　matrix,　the　decalcification　reactions　of　metal-bearing　CSH　results　in　successful　recovery　of　noble　metals　(Ag,　Au,　Pd)　upon　NaOH　etching　the　resultant　SiO2　support.　Further,　SiO2-based　heterostructures,　containing　nanocrystalline　metals　(e.　g.　Au0,　Ag0,　Pd0,　Fe0,　Co0,　Ni0,　Cu0,　and　Zn0)　or　rare-earth　oxides　(e.　g.　CeO2,　Y2O3,　and　Gd2O3),　are　formed　after　reduction　in　H2/Ar　(5　vol%　H2)　flow,　which　is　also　very　important　for　the　multipurpose　immobilization　of　diverse　hybrid　materials　on　SiO2　surface　(e.　g.　Cu0-Ag0@SiO2,　Cu0-CeO2@SiO2,　and　Cu0-Ag0-CeO2@SiO2).　©　2022　Elsevier　Inc.