Removal of Congo Red dye, polar and non-polar compounds from aqueous solution using magnesium aluminate nanoparticles

Chemical analysis of low carbon content coals and their applications as dye adsorbent

Coal is primarily a fuel material but lately it has been utilized as an adsorbent for removing toxic metal ions. However, its usage for removing organic pollutants is not well studied. We report here a systematic study on the use of coal samples of varying carbon contents as adsorbents for removing Basic Blue 41 as a model cationic dye. The coal samples were collected from coal mines and were thoroughly characterized. The concentrations of carbon, hydrogen, oxygen, nitrogen and sulphur contents were measured by CHNS analyzer. The concentrations of aluminum, silicon, sulphur, titanium and iron were determined by EDXRF, which corresponded to silicon dioxide (quartz) and aluminium silicate (kaolinite) as the major mineral inclusions, corroborated by XRD results and micrographs showing elemental maps determined from SEM-EDAX. The coal samples with low carbon content revealed higher adsorption capacity (q_e ∼ 8.0-9.3 mg/g) of Basic Blue dye at optimized adsorbent dose (2 mg/mL), pH 9 and contact time (120 min). The adsorption kinetic studies satisfied pseudo second order model and the intra-particle diffusion of the dye was evident. The dye adsorption followed Langmuir adsorption isotherm, and the q_max values ranged between 17 and 30 mg/g for low carbon content coal. The FT-IR, Brunauer-Emmett-Teller (BET) surface area and zeta potential results of the coal samples could explain the adsorption phenomenon of cationic dye. The kinetic and thermodynamic studies revealed that the adsorption of Basic Blue 41 dye was based on chemisorptions mechanism.

Biogenic synthesis of MgO nanoparticles from different extracts (flower, bark, leaf) of Tecoma stans (L.) and their utilization in selected organic dyes treatment

The occurrence and influence of dyes-containing effluents are alarmingly serious; hence, the treatment of such wastewater needs to be undertaken. Here, we report the biosynthesis strategy and utilisation of MgO nanoparticles (MgO NPs) from distinct Tecoma stans (L.) plant extracts (flower, bark, and leaf). The FT-IR spectroscopy revealed the dominance of chemical bonds as well as functional groups on MgO NPs surfaces. For adsorption experiments, the impact of pH, contact time, concentration, and pH on uptake efficiency of congo red (CR) and crystal violet (CV) dyes were investigated and then optimized using response surface methodology and Box-Behnken design. Under the optimal conditions, 99.7% CR (at C_i = 9.33 mg/L, Dos = 0.22, pH = 7.9) and 90.8% CV (at C_i = 5.0 mg/L, Dos = 0.3, pH = 6.3) were attained. The maximum adsorption capacities were calculated from 89.24 to 150.49 mg/g, where MgO NPs derived from flower extract gave better adsorption efficiency than those from other extracts. Therefore, MgO NPs material from Tecoma stans (L.) flower extract is expected as a perspective adsorbent for the effective remediation of organic dyes.