Lead removal from aqueous solution by means of integral natural clays honeycomb monoliths

[Display omitted] •Natural clay honeycomb monoliths as cheap tool to remove lead from aqueous solution.•Flow recirculation over honeycomb as alternative to batch experiments with powder.•Honeycomb has higher performance than powdered packed column under same conditions.•Adsorption equilibrium data and kinetics fit with Langmuir and second order models.•No direct correlation between Pb retention capacity and texture and CEC of clays. Different natural Moroccan clays were used as adsorbents for the removal of lead from aqueous solution. The study was performed not only employing the starting clays in the form of powder but also after their extrusion as honeycomb monoliths, this representing the major novelty of this work respect to the current state-of-art. The experiments were done in batch conditions with continuous stirring and using a recirculated flow, respectively. In addition to an exhaustive characterization of the clays by means of X-ray fluorescence, X-ray diffraction, thermogravimetric analysis, laser granulometry, N2 physisorption, infrared spectroscopy, SEM-EDS and evaluation of the cation exchange capacity, special attention was paid to the influence on the lead adsorption of variables such as adsorbent dosage, pH, contact time with the adsorbate and initial concentration of lead. Considering the cheap and abundant character of the raw materials, their easy processing (no additives were required for their extrusion) and the time and energy save due to no need for further modification through chemical/thermal activation, the obtained results (with retention over 90% for 30 ppm of lead) demonstrated the potential of the proposed design as low cost solution that may be competitive versus other technologies for water depollution, especially in developing regions.