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The removal of heavy metals from wastewater has become the subject of considerable interest at present. Thus, the use of novel adsorbents that are highly efficient is of critical importance for the removal of Cr (VI) ions from aqueous media. The adsorption of Cr (VI) ions from aqueous solutions by a new adsorbent, cedar wood sawdust, and the optimization of its adsorption parameters, were investigated in this study. Cedar wood sawdust was used in its native and HNO3/NaOH chemically modified forms as new low-cost sorbents to remove Cr (VI) ions from aqueous solutions in a batch system. The adsorption conditions were analyzed via response surface methodology. The RSM results showed that the optimal adsorption conditions yielding the best response were an adsorbent mass of 2 g for native Cedar and 1.125 g for its activated form, a metal concentration of 150 mg/L for native Cedar and 250 mg/L for activated, a temperature of 50 °C, a pH of 1, and a contact time of 67.5 min. At optimum adsorption conditions, the maximum adsorption capacities and the adsorption yields were 23.64 mg/g and 84% for native Cedar and 48.31 mg/g and 99% for activated Cedar, respectively. [ABSTRACT FROM AUTHOR]

Three Moroccan clays, denoted A1, A3 and A5, were sampled from the Fez region with the aim of potential use as aluminosilicate precursors for geopolymer synthesis. Each clay was subjected to calcination at 700 °C and analyzed using DTA/TG, grain size distribution measurements, XRD, and FTIR spectroscopy before and after heat treatment. The results showed that the three clays contain kaolinite in different proportions in addition to some associated minerals, such as quartz, hematite, calcite and dolomite. Heat treatment successfully activated the clay by the amorphization of kaolinite, which is essential for geopolymerization. Some other changes were observed in the associated minerals, especially carbonates, which partially or totally decomposed depending on the clay, while other minerals remained intact. The SBET and NBO values are in accordance with the degree of polymerization, and the obtention of consolidated materials is possible by alkali activation of the calcined clays.