Lignite-Activated Carbon Grafted PAA Combined with Conventional Drinking Water Treatment Processes for the Emergency Removal of Trace Pb(II) Pollution

In response to the emergency treatment of trace Pb(II) pollution, taking cost and coordination with existing conventional processes into account, based on the lignite upgrading by-products (waste) as raw materials, a low cost adsorbent lignite-based activated carbon/polyacrylic acid (LAC/PAA) was developed by the in situ grafting of PAA on the surface of LAC. The declination of the pH from 8.71 for LAC to 4.83 for LAC/PAA and FT-IR analyses of LAC/PAA before and after Pb(II) adsorption confirmed the appearance of carboxyl groups on the surface of LAC/PAA. The adsorption experiments reveal that more than 90% of Pb(II) were removed by LAC/PAA within 20 min (only 31% for LAC). Its adsorption behavior obeys the Freundlich isotherm model (R2 = 0.973), and the adsorption kinetics agrees with the pseudo-second-order kinetic model (R2 = 0.961). The performances for the removal of Pb(II) in XJ River (South of China) were investigated for LAC/PAA and the conventional water treatment processes, respectively. Based on the results, a combination process (LAC/PAA adsorption + conventional water treatment) was developed, which achieved the best Pb(II) removal (99.8%) under a lower LAC/PAA and coagulant dosages (both 20 mg/L) at a pH of 10, 3 times better than that of the conventional water treatment processes (only 30%). Undoubtedly, the above results will provide significant technical support for the emergency treatment of trace Pb(II) pollution of drinking water. Moreover, converting the lignite upgrading by-products (waste) into LAC will add considerable economic value and reduce the costs of waste disposal.