Efficacy of Adsorption of Congo Red Dyes from an Aqueous Media using Silicon Nitride (Si3N4) Adsorbent Derived from Sand and Coffee Husk Wastes

The current study utilizes Silicon Nitride (Si3N4) as a novel adsorbent in evaluating its adsorptive ability for Congo red dyes from an aqueous solution. The adsorbent was prepared using extracted silica from sand and coffee husk biochar in an ammonia environment. The Si3N4 adsorbent was characterized using a Field Emission Scanning Electron Microscope (FEI ESEM) which showed rod-like and fiber-like structures for α-Si3N4 and β- Si3N4, respectively. The SEM results also showed pores on the adsorbent surface before adsorption and a more rigid and restrained surface after adsorption. The adsorbent surface is hydroxylated in water to give important adsorption sites of silanolate ions (Si-O-) and silazane groups (Si2=NH2+) responsible for congo red (CR) dye removal. The adsorption process was investigated by batch mode. The maximum adsorption capacity (28.87 mg/g) was obtained at an optimal pH=1.00, agitation time (50 minutes), adsorbent dosage (25 mg), and initial concentration (50 mg/L). The Langmuir isotherm model was best fitted with equilibrium data with R2 > 0.9, showing that the adsorption was chemisorption in nature. The results revealed Si3N4 adsorbent as a potential adsorbent in textile dye wastewater treatment.