Bioavailability and mobility of arsenic, cadmium, and manganese in gold mine tailings amended with rice husk ash and Fe-coated rice husk ash.

This study was conducted to determine the effects of rice husk ash (RHA) and Fe-coated rice husk ash (Fe-RHA) on the bioavailability and mobility of As, Cd, and Mn in mine tailings. The amendments were added to the tailings at 0, 5, 10, or 20% (w/w) and the mixtures were incubated for 0, 7, 15, 30, 45, and 60 days. The CaCl2 extractable As, Cd, and Mn in the amended tailings were determined at each interval of incubation period. In addition, the tailings mixture was leached with simulated rain water (SRW) every week from 0 day (D 0) until day 60 (D 60). The results showed that both RHA and Fe-RHA application significantly decreased the CaCl2-extractable Cd and Mn but increased that of As in the tailings throughout the incubation period. Consequently, addition of both RHA and Fe-RHA leached out higher amount of As from the tailings but decreased Cd and Mn concentration compared to the controls. The amount of As leached from the Fe-RHA-amended tailings was less than that from RHA-amended tailings. Application of both RHA and Fe-RHA could be an effective way in decreasing the availability of cationic heavy metals (Cd and Mn) in the tailings but these amendments could result in increasing the availability of anionic metalloid (As). Therefore, selection of organic amendments to remediate metal-contaminated tailings must be done with great care because the outcomes might be different among the elements.

Removal of Zinc from Aqueous Solution by Optimized Oil Palm Empty Fruit Bunches Biochar as Low Cost Adsorbent.

This study aims to produce optimized biochar from oil palm empty fruit bunches (OPEFB), as a green, low cost adsorbent for uptake of zinc from aqueous solution. The impact of pyrolysis conditions, namely, highest treatment temperature (HTT), heating rate (HR), and residence time (RT) on biochar yield and adsorption capacity towards zinc, was investigated. Mathematical modeling and optimization of independent variables were performed employing response surface methodology (RSM). HTT was found to be the most influential variable, followed by residence time and heating rate. Based on the central composite design (CCD), two quadratic models were developed to correlate three independent variables to responses. The optimum production condition for OPEFB biochar was found as follows: HTT of 615°C, HR of 8°C/min, and RT of 128 minutes. The optimum biochar showed 15.18 mg/g adsorption capacity for zinc and 25.49% of yield which was in agreement with the predicted values, satisfactory. Results of the characterization of optimum product illustrated well-developed BET surface area and porous structure in optimum product which favored its sorptive ability.

Effects of pyrolysis temperature on the physicochemical properties of empty fruit bunch and rice husk biochars.

Biochar has received great attention recently due to its potential to improve soil fertility and immobilize contaminants as well as serving as a way of carbon sequestration and therefore a possible carbon sink. In this work, a series of biochars were produced from empty fruit bunch (EFB) and rice husk (RH) by slow pyrolysis at different temperatures (350, 500, and 650°C) and their physicochemical properties were analysed. The results indicate that porosity, ash content, electrical conductivity (EC), and pH value of both EFB and RH biochars were increased with temperature; however, yield, cation exchange capacity (CEC), and H, C, and N content were decreased with increasing pyrolysis temperature. The Fourier transform IR spectra were similar for both RH and EFB biochars but the functional groups were more distinct in the EFB biochar spectra. There were reductions in the amount of functional groups as pyrolysis temperature increased especially for the EFB biochar. However, total acidity of the functional groups increased with pyrolysis temperature for both biochars.

Comparison of the carbon-sequestering abilities of pineapple leaf residue chars produced by controlled combustion and by field burning.

This study was undertaken to compare the chemical properties and yields of pineapple leaf residue (PLR) char produced by field burning (CF) with that produced by a partial combustion of air-dried PLR at 340 °C for 3 h in a furnace (CL). Higher total C, lignin content, and yield from CL as well as the presence of aromatic compounds in the Fourier Transform Infrared spectra of the char produced from CL suggest that the CL process was better in sequestering C than was the CF process. Although the C/N ratio of char produced from CL was low indicating a high N content of the char, the C in the char produced from CL was dominated by lignin suggesting that the decomposition of char produced from CL would be slow. To sequester C by char application, the PLR should be combusted in a controlled process rather than by burning in the field.