The Removal of Pb2+ from Aqueous Solution by Using Navel Orange Peel Biochar Supported Graphene Oxide: Characteristics, Response Surface Methodology, and Mechanism

Co-pyrolysis of orange peel and eggshell for oxygenated rich composite: Process optimization with response surface methodology

Co-pyrolysis of orange peel and chicken eggshell was performed for the synthesis of the composite, a co-pyrolysis technique used to promote natural fabrication and to allow the raw material elemental combination effect and the preparatory conditions such as pyrolysis temperature, residence time, and eggshell/orange peel mixing ratio, to be optimized with the response surface methodology through Box-Behnken Design(BBD). BBD involved a randomized series of 17 experimental runs, and the best optimal conditions were found with a pyrolysis temperature of 300 °C, a residence time of 1 h, and 0.5 as the mixing ratio. These conditions gave a maximum adsorption capacity of 167 mg/g for removal of the modal pollutant methylene blue. FTIR spectra of the composite showed new functional peaks of oxygenated groups, at two different bands. XRD confirmed an amorphous surface with inorganic component peaks, while SEM-EDS revealed rich defects sites along with an enhanced percentage of oxygen elements on the surface; the surface area was enhanced from 1 m2 with unmodified peel to 64 m2 with composite. The adsorption behavior of the composite was studied for dye removal and the adsorption behavior was well explained by the Langmuir isotherm model.

The Removal of Cr(VI) from Aqueous Solutions with Corn Stalk Biochar

The discharge of wastewater containing hexavalent chromium (Cr(VI)) into the environment is very harmful to living things. Therefore, before effluent that contains Cr(VI) can be discharged into the environment, this toxin should be removed from the contaminated water. In this study, corn stalk biochar was investigated to evaluate the Cr(VI) removal efficiency from an aqueous solution. The effects of pH (2-10), biochar concentration (0.5 to 10 g/L), Cr(VI) concentration (10-500 mg/L), and contact time (10-1440 min) were studied. The actual experimental value of the Cr(VI) removal efficiency was 28.67%, largely consistent with the predicted model value of 29.31%, under the optimal conditions of a Cr(VI) concentration of 60 g/L, pH 4, contact time of 270 min, and a biochar concentration of 4.5 g/L. A significant interaction between the Cr(VI) concentration and pH was observed, along with significance in the interaction between Cr(VI) concentration and biochar concentration, which had a greater impact on the removal of Cr(VI). Biosorption onto corn stalk biochar is an affordable and economical adsorption process to treat wastewater contaminated with Cr(VI). The aim of this study is to provide data to serve as a basis for future studies on the use of raw agricultural waste to remove Cr(VI).