A synthetic clay (Mg/Al-layered double hydroxides; LDH) was directly synthesized through a simple coprecipitation method under a low-supersaturation condition. The clay was applied to remove metal cations (Cd2+, Cu2+, Pb2+, Ni2+, and Cr3+) and oxyanions (MnO4– and Cr2O72–) from a single aqueous solution. The result demonstrated that LDH exhibited a poor porosity (its specific surface area and total pore volume: 23.2 m2/g and 0.161 cm3/g, respectively) and positively charged surface within solution pH from 3.0 to 12. The X-ray powder diffraction (XRD) data suggested that the basal spacing of LDH was 0.773 nm. The presence of active CO32– anions in the interlayer region of LDH that played an extremely important role in the adsorption process was identified by XRD and Fourier-transform infrared spectroscopy (FTIR). Energy-dispersive X-ray spectroscopy (SEM) analysis indicated that LDH possessed a surface morphology like a plate with a hexagonal shape. The adsorption isotherms of LDH towards various potentially toxic metals were conducted at 1.0 g/L, pHEquilibrium 5.0, 30°C, and 24 h. The Langmuir maximum adsorption capacity of LDH towards the target metals exhibited the following order: 1.299 mmol/g (for Ni2+ adsorption) > 0.880 mmol/g (Cd2+) > 0.701 mmol/g (Cr3+) > 0.657 mmol/g (Pb2+) > 0.601 mmol/g (Cu2+) > 0.589 mmol/g (Cr2O72–) > 0.522 mmol/g MnO4–. The synthetic clay can adsorb both cations and anions in the solution. Therefore, such LDH material can serve as a potential dual-electronic adsorbent for effectively eliminating various oxyanionic and cationic metal ions from water media.

Learner autonomy (LA) has been concentrated in the Vietnamese educational context for more than two decades as it equips learners the capacity for lifelong learning. For the EFL tertiary context, students encounter various challenges practicing language skills, especially English speaking, because of lacking the language environment (Huyen & Cang, 2021). As the importance of LA and students’ English speaking skills in language learning, this study aims at exploring what EFL teachers support to develop LA in speaking English. The study using a mix-method approach was conducted at a university in the Mekong Delta with the participation of 12 EFL teachers. To gain insights into teachers’ support to develop LA in speaking English, a questionnaire, recording observations and a semi-structured interview were used to collect data from the participants. The result indicated that the teachers positively supported their learners by offering choices of relevant information belonging to English speaking topics delivered, implementing class discussion and group work activities, encouraging them to self-evaluate and emphasizing the importance of LA in speaking development.

The study was carried out from August 2019 to August 2020 at five major parks in Ho Chi Minh City. We aimed to survey the lighting system including bulb types, lamp types, illumination type, and average horizontal illuminance. The study was carried out by several methods such as a questionnaire of the characteristics of the lamp, observing, measuring, analyzing, synthesizing data, and evaluating. We divided each park by area, for example, main gate, side gate, main axis, branch road, lawn, activity area for investigation. The result showed that the parks having LED and HQ compact bulbs, which were popular chandeliers. Most parks had direct lighting to provide panoramic illumination, but did not reach the average horizontal illuminance. We propose an aesthetic illumination design for the central area of ​​the park with ideas from the history of the park's formation and development. The research results contribute to the improvement of the lighting system for the parks in Ho Chi Minh City.