For the purpose of volume reduction and detoxification of the low-grade aluminum dross (abbreviated as L-dross) with low content of metallic Al, the leaching behavior of two kinds of L-dross was investigated using 2 mol/dm³ H₂SO₄ and 2 mol/dm³ NaOH with or without heating operation. Ettringite with an anion removal ability was synthesized from the L-dross leachate generated after the volume reduction and detoxification treatment. A series of wet treatment process composed of L-dross leaching and ettringite synthesis was tried to develop in this study.

In the case of leaching with 2 mol/dm³ H₂SO₄, the Al³⁺ concentration in leachate and leaching percentage are increasing with an increase in leaching temperature in the order of 85°C > 50°C > Room temperature. On the other hand, the effect of heating on L-dross leaching using 2 mol/dm³ NaOH is not remarkable. In terms of volume reduction, it is found that the H₂SO₄ leaching with heating is effective and the residual ratio shows approximately 50 mass%.

According to the detoxification due to the dissolution of metallic Al and the hydrolysis of AlN, the heating effect appears to both leachates. The NaOH solution is found to be more valid than the H₂SO₄ for the acceleration of Al dissolution and AlN decomposition. Ettringite was synthesized easily from both leachates treated with 2 mol/dm³ H₂SO₄ and 2 mol/dm³ NaOH, by adding Ca(OH)₂ and CaSO₄ · 2H₂O. It is considered that the wet treatment process suggested in this study makes contribution to the volume reduction and detoxification of the L-dross and the synthesis of ettringite using the L-dross leachate.

In Japan, many studies have been conducted to reduce the cost of mine drainage treatment at abandoned mines. The treatment method called “passive treatment” that utilizes natural purification and is expected to be applied to mine drainage treatment.

Following the completion of the guidelines on the introduction of passive treatment, we conducted a simple screening focused on water quality, quantity and utilizable blank space to review the applicability of passive treatment to abandoned mines in Japan.

Our findings indicate that passive treatment has the potential to be applied to many of abandoned mines in Japan, although there are still some issues to be solved.

In this study, we prepare a sulfur-impregnated carbonaceous adsorbent from bamboo via mechanochemical treatment under an H₂S atmosphere. Bamboo is pyrolyzed at 400°C under a pure N₂ atmosphere to obtain carbonaceous bamboo and then treated with a planetary ball mill under a 10% H₂S atmosphere for mechanochemical treatment. Results show that sulfur-impregnated carbonaceous adsorbents with high nickel removal ability can be prepared, whereas bamboo without pyrolysis cannot be converted into sulfur-impregnated bamboo with high nickel removal. The Langmuir model is shown to be more applicable to the adsorption isotherm for Ni ions than the Freundlich model, and the calculated maximum adsorption amount is 0.186 mmol/g.