Efficacy of Adsorption of Congo Red Dyes from an Aqueous Media using Silicon Nitride (Si۳N۴) Adsorbent Derived from Sand and Coffee Husk Wastes

The current study utilizes Silicon Nitride (Si۳N۴) 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 Si۳N۴ adsorbent was characterized using a Field Emission Scanning Electron Microscope (FEI ESEM) which showed rod-like and fiber-like structures for α-Si۳N۴ and β- Si۳N۴, 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 (Si۲=NH۲+) responsible for congo red (CR) dye removal. The adsorption process was investigated by batch mode. The maximum adsorption capacity (۲۸.۸۷ mg/g) was obtained at an optimal pH=۱.۰۰, agitation time (۵۰ minutes), adsorbent dosage (۲۵ mg), and initial concentration (۵۰ mg/L). The Langmuir isotherm model was best fitted with equilibrium data with R۲ > ۰.۹, showing that the adsorption was chemisorption in nature. The results revealed Si۳N۴ adsorbent as a potential adsorbent in textile dye wastewater treatment.

Keywords:

Silicon Nitride (Si۳N۴) , Hydroxylation , Congo red (CR) , Efficacy , Kinetic , chemisorption