Biosorption of heavy metal ions can be an effective process for the removal of Cd(II) from wastewater. In this study, the batch removal of Cd(II) from dilute aqueous solution using Stereophyllum radiculosum as the biosorbent has been investigated. The Cd(II) uptake was dependent on the initial pH, contact time, initial metal ion concentration, and temperature. The residual Cd(II) in the solution was determined using Atomic Absorption Spectrophotometer. The optimum pH for the biosorption was pH 6. Maximum biosorption was obtained after 60 min of the process. Kinetic study showed that the pseudo-second-order rate equation best described the biosorption process. The adsorption isotherms obtained fitted well into the Freundlich and Langmuir isotherm. The Freundlich equation obtained was log À ¼ 2.6924 logC e þ 0.1131, while the Langmuir equation obtained was 1/À ¼ 0.0008/C e þ 17.41. The correlation factors obtained were 0.0995 and 0.9904, respectively. The free energy change obtained for the biosorption of Cd(II) at 300 K, initial Cd(II) concentration of 100 mg L À1 and pH 6 was À20.894 kJ mol À1 . The thermodynamic study showed that the increase in temperature led to increase in the amount of the metal ion biosorbed. These results indicate that S. radiculosum has potential for the uptake of Cd(II) from industrial effluents.

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This work presents a new optical microfluidic paper biosensor for the detection of organophosphate pesticides and carbamate pesticides. The assay strip is composed of a paper support (1×17.6 mm) onto which acetylcholine esterase (AChE) and acetylcholine chloride (AChCl) are deposited, in such a way that there is a small hole between them that ensures that they only come into contact in the reaction zone when they are carried by a solution of the sample by lateral flow to the reaction zone containing bromocresol purple (BCP) as the pH indicator, immobilized by sol-gel. The sensor operates at room temperature and the rate of the inhibited reaction serves as an analytical signal, which is measured using a camera by quantifying the appropriate colour coordinate. Calibration curves were obtained for chlorpyrifos and carbaryl, with a useful concentration range from 0.24 to 20 µg•L -1 for carbaryl and from 2.00 to 45 µg•L -1 for chlorpyrifos. The detection limits were 0.24 and 2.00 µg•L -1 , respectively, and with reproducibility around 4.2-5.5%. The method was applied to the determination of pesticides in different water samples, with no sample preparation.

Biosorbent prepared from the scale of croaker fish (Genyonemus lineatus) has been used for the removal of Pb(II) ion from aqueous solution in a batch system. The effects of some important parameters such as pH, initial metal concentration, temperature and biosorbent dosage on biosorption capacity were investigated. Equilibrium time for the biosorption process is 20 and 30 min at lower and higher concentrations, respectively. The process at 28 W C is in agreement with a pseudosecond-order kinetics model. The equilibrium data obeyed the Langmuir adsorption isotherm with a maximum monolayer adsorption capacity of 14.58 mg g À1. The study showed that the sorption process depends on biomass dosage, temperature, pH and initial metal ion concentration. The calculated thermodynamics parameters (ΔG o , ΔH o and ΔS o ) indicated that the biosorption of the metal ion onto fish scale is feasible, spontaneous and exothermic in nature.

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