Isaac W. Mwangi

Remediation of Some Selected Heavy Metals from Water Using Modified and Unmodified Mushrooms

The dispersal of toxic heavy metals by water from natural and anthropogenic is a worldwide environmental concern due to pollution. Despite some metals playing an important role in body, they are toxic when the level exceeds the tolerance limits while others such as lead have no known physiological value to human beings. Since heavy metals cannot be degraded, then their removal from drinking water is necessary. Mushrooms are readily available in Bomet County and their metal removal ability was investigated. The study aimed at removing heavy metals from water by adsorption using mushroom, as a cost-effective and sustainable method. The raw mushroom was modified with sodium hydroxide and characterization of both the parent material and its modified form was done using Fourier Transform Infrared spectrometry (FTIR). Sorption experiments were carried out using the batch adsorption method and sorption parameters including pH, contact time, adsorbent dose and initial metal ion concentration investigated. The results found out that the sorption capacity for cadmium ions ranged from 1.826- 25.285 mg/g by the unmodified edible mushroom (UEM), the modified edible mushroom (EM), unmodified toxic mushroom (UTM) and modified toxic mushroom (TM). For copper ions, sorption capacity ranged from 0.002-4.097 mg/g, while that of the lead ions ranged from 1.345-2.593 mg/g by the UEM, EM, UTM and TM respectively. The sorption capacity showed improvement on modification as sorption of cadmium increased from 1.826-25.285 mg/g by the UEM, EM, UTM and TM. At a pH range of 4-6, the sorbent material was found to remove up to 90% of the metals. The sorbent material had a removal efficiency of 95% of the metals in less than 20 minutes. The UEM and UTM fitted well in Langmuir adsorption isotherm model for cadmium and lead ions. For copper ions, UEM, EM, UTM and TM fitted in the Freundlich model. TM for lead ions best fitted in the Freundlich model. The bio-sorption kinetics was determined by fitting first-order-Lagergreg and Pseudo-second-order kinetics models to the experimental data. It was found that the data for lead was better described by the pseudo-second-order model. For copper ion, the data was best described by Ho’s pseudo second order for UEM and UTM, cadmium ions for all sorbents was best described by Lagergreg’s first-order kinetics. The FTIR analysis suggested the possibility of the participation of carboxyl groups in metal uptake. The levels of dissolved organic carbon (DOC) were found to be 19.0 mg/L in the raw material and 2.19 mg/L after modification. It was confirmed that modification minimized secondary pollution. This indicated that mushrooms have a potential application for the remediation of metal polluted waters.

Adsorption Studies of Lead, Copper and Cadmiun Ions in Aqueous Solution by Ethylene Diamine Modified Amberlite XAD-1180

This study reports on the synthesis of an adsorbent for the preconcentration of heavy metals at trace levels in environmental samples. Amberlite XAD resins are excellent support materials because of their high surface area and good mechanical stability. Ethylenediamine was chemically anchored on the resin to create active sites for metal adsorption. It was then employed for adsorption of lead, copper and cadmium ions in aqueous solution. Contact time flow rate and pH were optimized after which Langmuir and Freundlich isotherms were applied on the experimental data to establish the mechanism of adsorption. The sorption capacity for the three metals under study (Cu2+, Cd2+ and Pb2+) were 61.49, 16.17 and 14.01 mg g−1, respectively. It was observed that the resin adsorbed 95% of the metals in less than 10 min indicating that the affinity of the adsorbent to the analyte metals was high and adsorption took place instantly. The developed method was applied to an environmental water sample whose concentration was determined and thereafter spiked with Cd2+, Cu2+ and Pb2+ at varying concentrations. The maximum percent recoveries were determined as 28, 98 and 90% for Cd2+, Cu2+ and Pb2+, respectively. This indicated that the adsorbent has a potential application as a tool for trace metal analysis in environmental samples.