Physico-chemical Activation on Rice Husk Biochar for Enhancing of Cadmium Removal from Aqueous Solution

Abstract

The biochar was prepared from rice husk by pyrolysis at slow pyrolysis at 300, 400, and 500ºC. The obtained biochars were activated by combined physico-chemical methods. An alkaline solution of 1.63 M of KOH was used for chemical pre-activation and made second pyrolysis at the same condition as first pyrolysis. Adsorption efficiency was studied using the batch static method under laboratory conditions. Cd(II) ion removal efficiency of activated biochars was increased from 13-20% to 95-97% over non-activated biochar. The activated biochar at a pyrolysis temperature of 300°C showed the highest Cd(II) ion removal efficiency of 97% at 180 min of contact time. Cd(II) ion adsorption isotherms of activated biochar were fitted well both in Langmuir and Freundlich model. The maximum Cd(II) ion adsorption capacity of activated biochar pyrolysis at 300ºC was 45.87 mg g -1 , about six times higher than that of the non-activated biochar (7.76 mg g -1 ). The activated biochar increased the BET surface area from 7.71 to 11.57 m 2 g -1 . It has been suggested that the simplicity of the physico-chemical activation technique, technically feasible, eco-friendly, and cost effective, can stimulate high Cd(II) ion removal efficiency of rice husk biochar.

The Potentiality of Rice Husk-Derived Activated Carbon: From Synthesis to Application

“…On the other hand, chemical treatment includes the utilization of activating agents through impregnation followed by activation at a higher temperature under inert environments [1,50,[81][82][83][84]. However, the preparation of AC from RH by the utilization of combination of these methods known as "physicochemical activation" has also been successfully employed [85]. Figure 2 illustrates the preparation of AC through different methods.…”

Critical Review on Biochar‐Supported Catalysts for Pollutant Degradation and Sustainable Biorefinery

“…[40,46] However, after the process, a washing procedure is necessary to eliminate the agents applied in impregnation and their respective salts. [47] Apart from several advantages of chemical activation process, there are certain issues that limit their application to some level, including equipment corrosion, recycling of chemical, and generation of secondary pollutants. [46] The chemicals applied in activation process are highly corrosive in nature, and this property is enhanced at elevated temperatures.…”

Application of biochar-based catalysts in biomass upgrading: a review

“…24,25 For decades, various activation methods have been explored to prepare porous biochars with special morphologies. 15,43,[45][46][47] According to the activation agents used, the activation methods can be broadly divided into the following two categories: physical activation and chemical activation. 43 3.1.1.…”

“…11 However, aer chemical activation, a washing process is usually required to remove the impregnating agent and its salts, leaving behind an activated biochar with improved surface area and porosity. 15,19 Accordingly, several issues, such as equipment corrosion, chemical recycling, secondary pollution, etc., involved in the chemical activation process affect the application of chemical activation to some extent. 11 The variables during the chemical activation process, such as the activation temperature, the type and dose of activating agent, feedstock type, etc., signicantly affect the porosity, pore size distribution, and specic surface area of the activated biochar.…”

“…In order to improve the physicochemical properties of the as-prepared biochars, various activation and functionalization approaches have been investigated to extend their applications. 15,16 The physicochemical properties of biochar vary signicantly according to the raw biomass material type derived, the carbonization process, and activation or functionalization methods. [16][17][18][19] Aer activation or functionalization, the biochar shows several interesting properties, such as large surface area, multi-scale porous structure, and abundant surface functional groups.…”