ADSORBENT

The rising issue of domestic wastewater pollution, mainly from heavy metals and organic pollutants, poses significant risks to public health and environmental sustainability in Nigeria. Traditional treatment methods are often costly and energy-intensive, emphasising the need for affordable, eco-friendly alternatives. This study investigated the use of Picralima nitida stem bark residue as a sustainable biosorbent for removing iron (Fe3⁺), zinc (Zn²⁺), chemical oxygen demand (COD), and total dissolved solids (TDS) from domestic wastewater. The research focused on evaluating the adsorption efficiency, identifying optimal conditions, modelling the underlying mechanisms, and comparing the cost-effectiveness to commercial activated carbon. The study conducted an experimental investigation using batch adsorption tests in controlled laboratory conditions. P. nitida bark residue was washed, oven-dried, ground, and chemically activated before analysis. The adsorbent was characterised through Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface analysis. Parameters such as dosage, contact time, temperature, and pH were systematicallys varied to evaluate performance. Additionally, Langmuir and the Freundlich isotherm models were employed to interpret the equilibrium data. A cost analysis was also performed to assess the economic viability of the adsorbent. The results indicated that adsorption efficiency increased with longer contact time and stabilised after 90 minutes. The highest removal rates were 100% for Fe3⁺, 99.60% for Zn²⁺, 98.90% for COD, and 89.97% for TDS at near-neutral pH and ambient temperature. The equilibrium data conformed to the Langmuir isotherm (R² = 0.9940), indicating monolayer adsorption. Economically, the treatment cost was ₦19.50 per litre, which is roughly 30–40% lower than that of commercial activated carbon. The study concludes that Picralima nitida stem bark residue is an effective, cost-efficient, and sustainable biosorbent for domestic wastewater treatment, supporting Nigeria’s initiatives in sustainable waste utilisation and SDG 6 (Clean Water and Sanitation).

Chromium is one of the most notorious heavy metals released by various industries such as tanning and leather industries, manufacturing industries, catalyst and pigments, fungicides, ceramics, crafts, glass, photography, electroplating industry and corrosion control application. This study was aimed at sorption of chromium(VI) ion from aqueous solution by adsorbent derived from used tyres. Waste tyre was collected from Uwelu spare part market in Edo state. The collected tire was washed and rinsed with distilled water to remove debris, oven dried for 3hours at 180oC and ground into powder. This dried powder was carbonized and activated by charging into a muffle furnace for 2hrs at 500oC and then treated with 4M nitric acid. The efficacy of chromium removal of the adsorbent is determined by investigating the various parameters such as adsorbent dose, agitation time and shaking speed. The adsorbent was characterized by Scanning Electron Microscopy (SEM), Energy dispersive X-ray (EDX) and Fourier Transform Infra-Red (FTIR) spectroscopy. The total pore volume of the adsorbent was observed to bet P/P0=0.988646762:0.624668 cm3/g. The percentage of C and O was found to be 30.50% and 20.23%. Analysis of Variance for the response surface quadratic model showed that the Model F-value of 75.25 implies that the model is significant. The Lack of Fit F-value of 0.9763 implies that the Lack of Fit is not significant relative to the pure error. The high R-square value (coefficient of determination) of 0.9898 indicates that the fitted model predicts the metal ion removal with reasonable precision