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New hybrid clay adsorbent based on kaolinite clay and Carica papaya seeds with improved cation exchange capacity (CEC), rate of heavy metal ion uptake, and adsorption capacity for heavy metal ions were prepared. The CEC of the new material is ca. 75 meq/100 g in spite of the unexpectedly low surface area (≈9 m 2 /g). Accordingly, the average particle size of the hybrid clay adsorbent decreased from over 200 to 100 μm. The hybrid clay adsorbent is a highly efficient adsorbent for heavy metals. With an initial metal concentration of 1 mg/L, the hybrid clay adsorbent reduces the Cd 2+ , Ni 2+ , and Pb 2+ concentration in aqueous solution to ≤4, ≤7, and ≤20 μg/L, respectively, from the first minute to over 300 min using a fixed bed containing 2 g of adsorbent and a flow rate of ≈7 mL/min. These values are (with the exception of Pb 2+ ) in line with the WHO permissible limits for heavy metal ions. In a cocktail solution of Cd 2+ , and Ni 2+ , the hybrid clay shows a reduced rate of uptake but an increased adsorption capacity. The CEC data suggest that the adsorption of Pb 2+ , Cd 2+ , and Ni 2+ on the hybrid clay adsorbent is essentially due to ion exchange. This hybrid clay adsorbent is prepared from materials that are abundant and by a simple means that is sustainable, easily recovered from aqueous solution, nonbiodegradable (unlike numerous biosorbent), and easily regenerated and is a highly efficient alternative to activated carbon for water treatment.

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Thirteen N-butylpyridinium salts, including three monometallic [C 4 Py] 2 [MCl 4 ], nine bimetallic [C 4 Py] 2 [M 1Àx a M x b Cl 4 ]a nd one trimetallicc ompound [C 4 Py] 2 [M 1Ày-z a M y b M z c Cl 4 ](M = Co, Cu, Mn; x = 0.25, 0.50 or 0.75 and y = z = 0.33), were synthesized and their structure and thermala nd electrochemical properties were studied. All compoundsa re ionic liquids(ILs) with melting points between 69 and 93 8C. X-ray diffraction provest hat all ILs are isostructural. The conductivity at room temperature is be-tween1 0 À4 and1 0 À8 Scm À1 .S ome Cu-based ILs reach conductivities of 10 À2 Scm À1 ,w hichi s, however, probablyd ue to IL dec. This correlates with the opticalb andgap measurementsi ndicating the formation of large bandgap semiconductors.A te levated temperaturesa pproaching the melting points, the conductivities reach up to 1.47 10 À1 Scm À1 at 70 8C. The electrochemical stability windowso ft he ILs are between2.5 and 3.0 V.

Six N-alkylpyridinium salts [C n Py] 2 [MCl 4 ] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C 4 Py] 2 [MCl 4 ] compounds are monoclinic and crystallize in the space group P2 1 /n. The crystals of the longer chain analogues [C 12 Py] 2 [MCl 4 ] are triclinic and crystallize in the space group P1. Above the melting tem-[a]5640 perature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl 4 ] 2ions in the Cubased ILs have a distorted tetrahedral geometry.

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