Activation of Natural Coal for Selective Preconcentration of Pb(II) Ions Prior to Its Trace Determination in Aqueous Samples by Flame Atomic Absorption Spectrometer

Natural coal was collected from Thar coal field, block IX in Province Sindh, Pakistan. The Thar coal was modified to Activated Thar Coal Adsorbent (ATCA) by reacting with concentrated H2SO4, which enhanced its porosity by dehydration as concentrated H2SO4 is strongly dehydration agent. The surface oxidation of coal was carried out by refluxing in concentrated HNO3. The ATCA was subjected to FT-IR spectrometer for characterization, which revealed the presence of COand COOHmoieties onto its surface. The ATCAwas packed in columnfor adsorption of Pb(II) ions and recovered >= 95.6% with relative error <= 4.4% and RSD <= 3.7% at pH 7.0, ATCA dosage 400 mg, sample volume 400 mL (flow rate of 2.0 mLmin(-1)) and eluent solution 5.0 mL of 0.5 mol L-1 HCl (flow rate of 1.0 mLmin(-1)). LOD (0.03 mu g L-1) and LOQ (0.11 mu g L-1) ofmethod were calculated followed by blank recording (n= 15) with preconcentration factor (PF) of 80. A linear response was observed with regression equation of y= 0.0934x+ 0.0411 and R-2= 0.99 for concentration range of 0.5-5.0 mg L-1 (before preconcentration). Similarly, a linear response was also observed with regression equation of y = 7.4358x + 0.0429 and R-2 = 0.99 for concentration range of 0.005-0.050 mg L-1 (after preconcentration). Breakthrough curve was plotted for obtaining total saturation capacity (152.5 mg g(-1)) of ATCA for adsorption of Pb(II) ions. Themethodworkedwell on realwater sampleswith recovery >= 92 +/- 4.5% of Pb(II) ions.