Characterization and Optimization of Neem Leaves and Moringa Seed Husk-based Composite Activated Carbon for Efficient Adsorption of Methylene Blue Dye

Abstract

The research in question was meticulously conducted within the premises of the Nigerian Liquefied Gas (NLG) Engineering laboratory, situated at the esteemed University of Maiduguri, Nigeria. This study focuses on the development and characterization of a composite material derived from neem leaves (NL) and Moringa seed husk (MSH) to adsorb methylene blue (MB) dye effluent. The synthesis process involved pyrolyzing MSH and NL at 400°C to produce MSH and NL biochar. These biochars were further treated with sodium hydroxide (NaOH) and potassium hydroxide (KOH) as activating agents, each separately. The physicochemical properties of NL and MSH were thoroughly examined through analytical techniques including Fourier transform infrared (FTIR) analysis, Energy Dispersive X-ray Spectroscopy (EDS), and Scanning Electron Microscopy (SEM). These analyses were conducted to gain comprehensive insights into the properties of the resulting adsorbent material. To optimize the adsorption process, Response Surface Methodology (RSM) was employed to determine the optimal operating conditions, thereby maximizing the adsorption capacity. Various factors including pH, contact time, temperature, concentration, and dosage were systematically investigated for their impact on the adsorption properties of methylene blue Dye Effluent. Experimental results indicated that the activated carbon produced by impregnating with KOH outperformed the one impregnated with NaOH. Specifically, the most favorable results were achieved at an initial MB concentration of 400 mg/l, utilizing 0.7 g of residue, and agitating at a rate of 250 rpm for one hour, yielding an efficiency of up to 95%. The study further delved into the adsorption equilibrium and kinetics of methylene blue dye on this composite activated carbon at a temperature of 30°C. The adsorption isotherm for methylene blue was effectively correlated with the Isotherms model, the Langmuir model, suggesting a monolayer coverage of adsorbate on a homogeneous adsorbent surface. Additionally, the kinetic analysis indicated that the adsorption process followed the pseudo-second-order model, implying that the rate-limiting step is chemisorption.