Sulfide mineral mining produces highly sulfate-contaminated wastewater which needs to be treated before disposal. A composite material was made from natural zeolite (NZ) and Superfloc^® SC-581, a polyammonium cationic polymer. The resulting modified zeolite (MZ) demonstrated improved capacity for sulfate abatement from wastewater compared to NZ. Above pH 4.0, MZ retained positive surface charge while NZ remained negative. The effect of the ionic strength on the adsorption process was evaluated. Sulfate adsorption capacity was assessed and revealed MZ to be superior to NZ in all cases. Adsorption kinetics reached equilibrium after 10–12 h, with MZ adsorption being twice that of NZ; data fitted a pseudo-second order kinetic model. Adsorption isotherms reflected the high capacity of MZ for sulfate adsorption with maximum of 3.1 mg g⁻¹, while NZ only achieved 1.5 mg g⁻¹. The process corresponds to heterogeneous partially reversible adsorption of ionic species over the solid adsorbent. Langmuir–Freundlich parameters revealed that adsorption over MZ corresponds to an interaction eight times stronger than that on NZ. The sulfate adsorption pattern changes with ionic strength. Taken together, the composite formed between natural zeolite and polyammonium represents an adsorbent that maintains the adsorption capacity of zeolite and proves suitable for anionic species removal. Further prospect considers the testing of the composite with other anionic pollutants (arsenate, phosphate, perchlorate, etc.)

The magnetic separates from the sand fraction of three Chilean soils forming on volcanic materials were studied by powder XRD, RT and 80 K Mössbauer spectroscopy, saturation magnetization measurements, and scanning electron microprobe analysis. Soil samples were collected from the B-horizon of pedons from native and cultivated areas. Results, particularly from powder x-ray diffractometry, Mössbauer spectroscopy, and chemical analysis, reveal relatively complex magnetic mineral assemblages in all samples. Fe (>70 mass% Fe2O3), Ti (ranging from ~2 to ~26 mass% TiO2), Al (from 1 to ~6 mass% Al2O3) and Mg (from 1 to ~6 mass% MgO) are the main elements found in the iron oxide-spinel structures. In at least one sample, namely the magnetically separated portion from the sand fraction of the fertilized Collipulli soil, the 80 K Mössbauer spectrum indicates that magnetite undergoes the Verwey transition. This sample, with saturation magnetization being of order of 40 J T−1 kg−1, is also the most magnetic of all magnetic separates. Results on the iron oxide spinels, from electron microprobe data, reveal a large variability not only of chemical composition, but also of crystalline structure and magnetic properties of these magnetic minerals. The effect of agricultural practices, particularly the continuous chemical fertilization and soil acidity correction over several years, on the iron oxide mineralogy could not be unequivocally established, but the present data provide a relatively detailed description of the magnetic iron oxide assemblages of these Chilean volcanic soils.