In this study, the iron-carbon-aluminum (Fe-C-Al) composite filler was prepared by aluminum modification of conventional iron-carbon (Fe-C) micro-electrolysis with a no-burn method. The optimal process conditions for Fe-C-Al three-phase micro-electrolysis treatment of low concentration phosphorus wastewater were determined to be the aluminum metal ratio of 14 wt% and solids dosing of 30 g/L. Under the optimal process conditions, Fe-C-Al three-phase micro-electrolysis was performed for the treatment of low concentration phosphorus wastewater (LCPW) with continuous experiment, while iron-carbon fillers before and after treatment were analyzed by XRD and SEM. The results showed that the amount of Fe2+ dissolved in the micro-electrolysis determined the micro-electrolysis phosphorus removal effect, Al promoted the dissolution of Fe2+, and the Fe-C-Al filler had a stable phosphorus removal effect, and the average removal efficiency of phosphorus was 67.40%, which is an average improvement of 29.25% compared with the conventional Fe-C filler. The treatment of LCPW by Fe-C-Al three-phase micro-electrolysis is consistent with a first-order kinetic reaction with apparent activation energy of 38.70 kJ·mol−1, which is controlled by the chemical reaction.

No abstract

To provide a scientific basis for the resource utilization of chromium slag, this article studies the release law of hexavalent chromium in the aged calcium-free chromium slag. XRD (X-ray diffractometer) and MLA (Mineral Liberation Analyzer) were used to analyze the composition of the chromium slag; using sulfuric acid-nitric acid as the leaching solution, the release law of hexavalent chromium in chromium slag and the leaching kinetics were studied. The results show that main components of the chromium slag are magnesioferrite, chromite, hematite, hydrargillite, and spinel; chromium is mainly present in chromite and magnesioferrite; the leaching rate of hexavalent chromium increases with the increase of temperature or the decrease of pH. The analysis of leaching kinetics shows the leaching rate is controlled by the internal diffusion reaction, and the apparent activation energy is 11.93 kJ·mol–1. The chromium slag is aged in high temperature seasons, which is conducive to the precipitation of hexavalent chromium in the chromium slag, can increase the yield of chromate in the roasting kiln, and is conducive to resource utilization; chromium slag should be stored in order to prevent acid rain erosion which leads to environmental pollution risk (e.g. drinking water).