A new carbon–diatomite earth composite adsorbent for removal of heavy metals from aqueous solutions and a novel application idea

•New carbon-silica composite adsorbent was prepared for removal of heavy metal ions.•Precursors and procedure are low cost, composite and adsorbed ions can be recycled.•Porous composite has high adsorption capacity in both of the closed and flow systems.•Composite was used in packed column as fractionation SPE effectively and repeatedly.•The bonding of metal ions to C–O bonds was demonstrated by SEM-EPMA techniques.

A new type of carbon coated diatomite earth (DE) composite adsorbent was prepared using cellulose as carbon source. Carbonization and functionalization were studied by various reactants and finally concentrated sulfuric acid was applied in one-step. The procedure resulted in highly functionalized, porous carbonaceous matter. Cellulose was substituted by low-cost material containing cellulose resulting in unremarkable difference in the properties of the composite. The composite was studied among others, by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) and elemental and correlation map was created by the obtained data. The composite was successfully used to remove heavy metal ions {Pb(II) and Ni(II)} from aqueous solution. The application was performed in both of the closed and flow systems. In closed system, the adsorption process followed the Langmuir isotherm. The adsorption depended on the pH and the highest adsorption capacities were 80 and 380 mg g−1 for Ni(II) and Pb(II) respectively. As a novel application, fractionation solid phase extraction (SPE) technique was applied for investigation of absorption characteristics of the composite in flow system. SEM-EPMA results demonstrated that lead was bonded to C–O bonds on the surface of composite.

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