The Influence of pH and Organic Matter from Sugarcane By-products on Soil Cadmium Fractionation

ABSTRACT

Crop wastes or by-products can have the potential to be used as effective amendments to improve agricultural soil quality and/or crop yields subject to appropriate screening and testing. Sugarcane (Saccharum officinarum L.) waste by-products from an ethanol production plant, including boiler ash, filter cake, and vinasse, were applied as soil amendments at 5%, 10%, 20%, and 40% (w/w) to study the relationship between pH and organic matter (OM) on cadmium (Cd) bioavailability and adsorption via organic matter using the Cd sequential extraction procedure. Soil pH was significantly affected by aging of the treatment with boiler ash, filter cake, and vinasse. At the end of the experiment, the Cd concentrations with all treatments were mainly released in the first two extraction steps of the sequential procedure, i.e., most mobile and easily mobilized fractions. Pearson correlation analyses revealed a negative relationship between pH and bioavailable Cd and between OM and oxidizable Cd. The pH reduction induced by the amendments was a major factor affecting soil Cd bioavailability. The effect of OM on Cd fractionation could not be clearly observed and interpreted in this study.     

Microemulsion-based palm kernel oil extraction using mixed surfactant solutions

This study introduces a novel technique using surfactant microemulsion-based oil seed extraction. To achieve this objective, microemulsion formation with palm kernel oil was studied first. Then, the selected microemulsion system was used for palm kernel extraction. The results showed that the mixed surfactant of 3 wt% Comperlan KD and either 0.1 wt% Alfoterra145-5PO or 145-8PO provided an ultralow interfacial tension with the palm kernel oil (0.0197 and 0.0359 mN/m, respectively). By using those two aqueous surfactant systems for palm kernel oil extraction, the extraction efficiency was 93.99 and 94.13% at the optimum crushed kernel size between 0.212 and 0.425 mm, using 1 g seed load to 10 ml of solution and 30 min of contact time. The extracted oil quality was evaluated for water content, fatty acids composition and surfactant partitioning into oil phase. The results showed that the quality of the oil obtained using the surfactant microemulsion-based technique is of similar or better quality than when extracted by hexane solvent.     

Fractionation of Cd and Zn in Cd-contaminated soils amended by sugarcane waste products from an ethanol production plant

Purpose

Sugarcane waste products (boiler ash, filter cake, and vinasse) from an ethanol production plant were used as soil amendments by adding 3 % (w/w) in single and/or in combination, with a research focus towards stabilization of cadmium (Cd) and zinc (Zn) in contaminated soils. The objective of this laboratory study was to evaluate the effects of adding these sugarcane waste products on bioavailability of Cd and Zn over time (aging) in Cd- and Zn-contaminated agricultural soils of Thailand.

Materials and methods

Two agricultural contaminated soils of low (<3 mg kg^?1) and high (10–15 mg kg^?1) Cd concentrations were collected from Tak Province, Northwest Thailand. Fourteen treatments were sampled at 2-week intervals for 84 days for metal bioavailability using BCR extraction procedures (proposed by The Standards, Measurements and Testing Programme of the European Union, SM&T) that determined exchangeable (BCR1), reducible (BCR2), oxidizable (BCR3), and residual (BCR4) fractions, and total concentration was determined using aqua regia digestion and microwave digestion.

Results and discussion

Cd was potentially bioavailable, predominantly in exchangeable (BCR1) and reducible (BCR2) fractions, while the higher contribution of Zn was more prevalent in refractory fractions (BCR2 and BCR4). Aging had an influence on fractionation of Cd and Zn, most notably in the first two fractions (BCR1 and BCR2) of BCR sequential extraction, which resulted in reduction of exchangeable Cd during the first few weeks of incubation (T?=?0 to 28 days). At the end of pot experiment, the exchangeable Cd fraction in the low Cd (LCdS) soil was reduced from 2.3 to 4.7 % and 9.4 to 39.9 % in low and high Cd (HCdS)-contaminated soils, respectively, as compared to nonamended soils.

Conclusions

The observed reduction in exchangeable Cd (BCR1) in the amended soils at the 3 % (w/w) application rate, the low total metal concentrations, and the significant amount of essential plant nutrients (N, P, and K) within these waste products highlight the benefits of amending metal-rich soils with them.