Biosorption of iron(ii) and manganese(ii) using Pleurotus Ostreatus spent mushroom compost in a continuous flow fixed bed column / Ain Nihla Kamarudzaman

Heavy metals pollution poses a major threat to human health and the environment.
Unlike many other pollutants, heavy metals cannot be biologically degraded to more
or less toxic products and persistent in the environment. Conventional technologies for
removing heavy metals are not economical and tend to generate huge quantity of toxic
chemical sludge. Biosorption is an alternative treatment technology for not only
removal but also recovery of heavy metals from industrial effluents. In this study, the
potential of Pleurotus ostreatus spent mushroom compost from mushroom cultivation
farm for iron(II) and manganese(II) removal were studied in a column operation
mode. The characterisations of Pleurotus ostreatus spent mushroom compost were
investigated using surface analyser, Scanning Electron Microscope, Energy Dispersive
X-ray Spectroscopy and Fourier Transformed Infrared Spectroscopy. Biosorption
performance studies for removing of iron(II) and manganese(II) were conducted in
single and binary mixtures heavy metals systems. For optimisation studies, various
experimental parameters were studied including flow rate (1 - 20 mL/min) with
surface loading (1.27 - 25.48 cm3/cm2.min), bed height (100 - 300 mm) and initial
heavy metals concentration (10 - 100 mg/L). The regeneration study was performed
by pumping 0.5 M HNO3 at a flow rate of 10 mL/min for five successive biosorption -
desorption cycles. The performance of Pleurotus ostreatus spent mushroom compost
for treating steel industrial effluent was also investigated in this study. The
experimental data were also analysed using Thomas, Yoon - Nelson, Modified Dose -
Response and Bohart - Adams models. Results from characterisation indicated that the
Pleurotus ostreatus spent mushroom compost biosorbent has a surface area of 0.7209
m2/g and the hydroxyl, carboxyl, amino and amide were identified as functional
groups involved in the biosorption of heavy metals. The optimal iron(II) and
manganese(II) biosorption operating conditions were achieved at a flow rate of 1
mL/min (surface loading of 1.27 cm3/cm2.min) and bed height of 300 mm. The results
also inferred that the breakthrough time, exhaustion time, retention time as well as the
iron(II) and manganese(II) uptake capacities and percentage of removal are highly
influenced by different flow rate, bed height and initial heavy metals concentration.
The binary mixtures heavy metals biosorption indicated that the active binding sites
on the surface of Pleurotus ostreatus spent mushroom compost had a strong affinity
for iron(II) compared to manganese(II). However, the biosorption of iron(II) and
manganese(II) in the binary mixtures heavy metals systems were significantly lower
compared to the single heavy metal system. The Pleurotus ostreatus spent mushroom
compost column was successfully reused for at least five biosorption - desorption
cycles for the removal and recovery of iron(II) and manganese(II) ions. The bed
column also efficiently remove different heavy metals from the steel industrial
effluent in application study. In this study, the experimental data were successfully
fitted to the Modified Dose - Response model and compared to other models, and the
maximum uptake capacity obtained from the experimental was also very close to the
value predicted by the Modified Dose - Response model. A new mathematical model
also developed in this study for a better description of biosorption performance and
prediction of breakthrough profiles for biosorption of heavy metals. It was concluded
that biosorption using Pleurotus ostreatus spent mushroom compost in a fixed bed
column could be an effective method for iron(II) and manganese(II) removal.