This study focused on the liquid phase sorption of methylene blue (MB) using low cost agro-waste from moringa pod husks. Moringa pod husk was carbonized at 450°C for 30 min, which was later activated with 0.1 M phosphoric acid. The physico-chemical properties of moringa pod activated carbon (AMP) were determined. The results of the physicochemical parameters are: moisture content (13.6 ± 0.02), ash content (2.61 ± 0.11), point of zero charge (pH ZPC) (7.2) and bulk density (0.6 g L-1). The sample was also characterized using Brunaeur Emmett Teller (BET), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier-transform infrared spectroscopy (FTIR). The BET surface area obtained for AMP is 1340.234 m 2 g-1. The effect of optimized parameters such as initial concentration, contact time, pH, adsorbent dosage, and temperature on methylene blue removal was investigated. The obtained maximum monolayer adsorption capacity value (q max) is 9.5785 mg g-1. The three adsorption isotherm models, namely Langmuir, Freundlich and Temkin, were employed to describe the fitness of equilibrium data. The Langmuir equation fitted the adsorbent system better with a R 2 value of 0.9958. The pseudosecond-order kinetic equation also fitted the data well. Thermodynamic studies showed that the AMP-MB adsorption system is spontaneous and endothermic as a negative and positive value was obtained for G 0 (-0.460 KJ mol-1) and H 0 (4.482 KJ mol-1), respectively.
ABSTRACT:The adsorption of Mn(II) and Co(II) ions from aqueous solution was investigated using batch adsorption experiment at room temperature. The effect of pH, contact time, metal ion concentration and temperature were evaluated. The residual concentrations of the metal ions were determined by atomic absorption spectrophotometer. The results showed that maximum removal of Mn(II) and Co(II) ions occurred at pH 9. Some physico-chemical and spectroscopic characterization of the adsorbents were done such as moisture content, ash content, bulk density, volatile matter, iodine number, point of zero charge (PZC), XRF, and FTIR. The moisture and ash content of MCAC adsorbent were found to be 9.85±0.06 and 5.5±0.1% respectively. The bulk density was found to be 0.37±0.01g/m 3 , iodine number of 367.66±30 mg/g and PZC of 6.8. The SEM micrograph shows particle grains and jelly like rough surfaces, FTIR analysis results show different functional group in the MCAB adsorbent such as O-H, C=O, and C=C stretching. Kinetic study shows that the pseudo-second order kinetic model best described the adsorption of metal ions. The equilibrium data fitted Langmuir, Freundlich and Temkin adsorption isotherms, in each case, the Langmuir model appears to have better regression coefficients than the Freundlich and Temkin. Thermodynamics investigation showed that Gibb's free energy change ( ) was negative indicating that the adsorption of Mn(II) and Co(II) ions by maize cob activated carbon were feasible and spontaneous. The positive value of enthalpy change ( ) implies that the reaction was endothermic while positive value of entropy change ( ) implies an irregular increase in the randomness at the solid/solution interface of the adsorbent during the adsorption process. © JASEM http://dx.doi.org/10.4314/jasem.v19i4.22
This work was carried out to assess the physicochemical parameters and removal of heavy metals from industrial wastewater by activated carbon prepared from calabash seed. Some physicochemical parameters of the wastewater that assessed are pH, temperature, and turbidity, BOD, COD, TS, TDS and TSS. Adsorption studies on the effects of contact time, pH and adsorbent doses on the removal of heavy metals were investigated. The pH and temperature of granite industrial wastewater were 7.5 and 32.5 respectively which are within the permissible limit of WHO (7-8.5 and 32 o C). The wastewater sample shows extremely high turbidity of 2.5 mg/l, biochemical oxygen demand (BOD) of 430 mg/l, chemical oxygen demand (COD) of 283 mg/l, total solid (TS) of 45 mg/l, total dissolved solid (TDS) of 655 mg/l and total suspended solid (TSS) of 965 which are above permissible limit of WHO. The maximum adsorption capacity of Zn (99%) and Fe (88%) were observed at pH 8 and 12 respectively. The pseudo-fist order and pseudo-second order kinetic models were used to fit the kinetic data of the adsorption process, and the result obtained showed that pseudo-second order kinetic model was able to fit the generated adsorption data from the heavy metals considered in this research work due to the regression coefficient R 2 of 0.997 value obtained. The study reveals that granite industrial wastewater effluent is one of the industries responsible for polluting the surrounding aquatic environment.
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