Electronic waste has become a global concern, as it has been steadily increasing over the years. The lack of regulation and appropriate processing facilities has rendered these wastes an environmental hazard. However, they represent excellent alternative sources of precious metals, which are highly in demand in various industries. Adsorption has been a popular method for metal removal/recovery because of several advantages, such as ease of use and low cost. In this regard, it is crucial to develop an inexpensive and functionalized adsorbent to selectively adsorb precious metals. Thus, silica, which is derived from rice husk and is abundantly present in Indonesia, was functionalized using an ionic liquid (SiRH_Im) and used for Au(III) adsorption from a simulated mobile phone leach liquor. SiRH_Im exhibited a high adsorption capacity (232.5 mg g-1). The Au(III) adsorption kinetic suitably fitted with the pseudo-second-order kinetic model. The Au(III) adsorption followed a chemisorption route that suited the monolayer model. Thomas' and Yoon-Nelson's models were well suited for the continuous Au(III) behavior. Selective recovery of Au(III) from SiRH_Im was achieved via sequential desorption. SiRH_Im also showed excellent reusability, as indicated by a negligible decrease in adsorptive performance over three cycles. The functionalization of silica derived from rice husk using an ionic liquid led to the successful creation of a solid adsorbent with a high adsorption capacity toward precious metals present in a simulated leach solution. Our results highlight the benefit of the functionalization of biomass through the immobilization of an ionic liquid toward the enhancement of its adsorption capability.
Theophylline (TP) is a methylxanthine derivative, which serves as a valuable compound in treating respiratory disorders and acts as a bronchodilator agent. However, TP has a limited therapeutic range (20-100 μmol L-1), demanding precise monitoring to prevent potential drug toxicity even with slight level fluctuations during treatment. Thus, to overcome this limitation, electrochemical methods have been extensively used due to their efficacy in achieving sensitivity, selectivity, and accuracy. In the context of electrochemical sensors, nanocarbon-based materials have gained widespread recognition for their extensive applications. Therefore, this review aims to explore the latest advancements in carbon-based electrodes particularly used for the precise determination of TP through electrochemical methods. The results are expected to provide insights into the profound significance of the methods in enhancing the accuracy and sensitivity for the detection of TP.