BACKGROUND In this study three natural Yemeni zeolites (NZ1, NZ2 and NZ3) having major minerals such as clinoptilolite and mordenite, were evaluated as low cost sorbents for the removal and recovery of ammonium ions. RESULTS The zeolite samples, with pHPZC = 9.1 ± 0.2, 7.9 ± 0.2 and 7.4 ± 0.2 for NZ1, NZ2 and NZ3, respectively, showed high ammonium sorption capacities. At pH 8, for treated waste waters: (i) with low NH4+ levels (from 25 to 100 mgNH4/L); and (ii) for concentrated NH4+ side streams generated from the anaerobic digestion of sewage sludge (from 400 up to 1500 mg L‐1), maximum loading capacities of 27 to 51 mgNH4 g‐1 were measured for the studied zeolites. Measured sorption isotherms, in the concentration range 0.05 to 5 g L‐1, were well described by the Langmuir isotherm. The ammonium sorption kinetics was controlled by particle diffusion and was well described by both the homogeneous diffusion (HPDM) and shell progressive (SPM) models. CONCLUSION Comparison of the equilibrium data with results for natural and synthetic zeolites demonstrate the higher performance of the studied zeolites providing low residual ammonium values <1 mgNH4 g‐1 and <10 mgNH4 g‐1 when treating both diluted and concentrated‐NH4+ streams, respectively. © 2017 Society of Chemical Industry

The paper deals with a formation of artificial rock (clinker). Temperature plays the capital role in the manufacturing process. So, it is useful to analyze a poor clinker to identify the different phases and defects associated with their crystallization. X-ray fluorescence spectroscopy was used to determine the clinker's chemical composition. The amounts of the mineralogical phases are measured by quantitative XRD analysis (Rietveld). Scanning electron microscopy (SEM) was used to characterize the main phases of white Portland cement clinker and the defects associated with the formation of clinker mineral elements. The results of a study which focused on the identification of white clinker minerals and defects detected in these noncomplying clinkers such as fluctuation of the amount of the main phases (alite (C3S) and belite (C2S)), excess of the free lime, occurrence of C3S polymorphs, and occurrence of moderately-crystallized structures are presented in this paper.