Utilizing cheap sawdust by-products of the timber industry waste to assess adsorption kinetics for improved cationic dye pollutant removal

Abstract

As an example of wastewater for appropriate disposal, inexpensive, easily accessible sawdust waste was modified and then evaluated experimentally to an adsorbent to remove pollution caused by Basic Red 2 (BR2) dye. Investigations were conducted on the use of natural sawdust (NSD) and activated sawdust (ASD) to remove BR2 dye from an aqueous medium. To chemically modify the ASD, 1 M caustic soda solution (NaOH) was used. By adding novel functional groups (–ONa) to the ASD surface, the sorption efficiency of the BR2 dye was improved. This resulted in a considerable increase in surface polarity and sorption site power. Using FTIR, EDX, and (SEM) analysis, the structure and morphology of adsorbent sawdust were examined. The batch technique generated quantitative adsorption under a range of circumstances, including initial concentration, pH, temperature, and contact time. The adsorption kinetics were investigated using two kinetic models, including pseudo first order and pseudo second order, and a pseudo second-order kinetic is the best model. Two common isotherm equations (Langmuir and Freundlich) are that were used to determine the BR2 dye adsorption isotherms on adsorbents and showed a good fit with the Langmuir model more than Freundlich’s isotherm model (R² = 0.995). The thermodynamic assessment demonstrated the exothermic, spontaneous, and feasible nature of the BR2 adsorption onto NSD and ASD. The results clarified that a large percentage removal and the optimized conditions were (8 ± 0.01) solution pH, 19.28 mg/L initial dye concentration, adsorbent dose 0.1 g/40 ml of dye solution for NSD and ASD respectively, and 60 min adsorption time. 68.72% and 93.77% of dye were removed by NSD and ASD respectively at experimental optimum conditions. The removal price per gram of BR2 dye in 1000 m³ of wastewater using ASD adsorbent was found to be 0.017$ which is very low compared to another adsorbent. The BR2 removal efficiency is still above 85% and 60% after four cycles concerning ASD and NSD respectively. Additionally, NSD and ASD are easily regenerative and reusable, suggesting that this adsorbent may have significant promise for wastewater dye adsorption. It was found that ASD removed contaminants more effectively than the other.

Graphical abstract