Bio-efficacy of imidazolinones in weed control in a tropical paddy soil amended with optimized agrowaste-derived biochars.

Biochar is a black carbon sorbent that has the ability to stabilize organic substances in soil and, therefore, the potential to reduce their bio-availability. This sustainable material can be produced from locally-available agro wastes. The present study, for the first time, investigated the effects of biochars produced from oil palm empty fruit bunches (EFB) and rice husk (RH) on the efficiency of imazapic and imazapyr (two polar members of imidazolinone herbicides) as well as Onduty®, a mixture of them. It was executed in a Malaysian paddy field soil during a 30-day greenhouse experiment. The presence of optimized EFB and RH biochars in the heavy soil generally increases weed seeds germination and plants growth due to stabilization of the herbicides. The effect of EFB biochar was found higher than RH biochar having a higher affinity to the herbicides. An increase in the biochars application rates enhanced their effects as a soil modifier. Differences were more significant in the higher herbicides doses. Efficacies of all the herbicides were generally decreased in the biochar-amended soils. In the presence of 0.5% biochar in soil, the GR50 values for all herbicides were almost similar to biochar-free soil. In a 1.0% biochar-soil mixture, GR50 values of the herbicides increased by about 1.5 times. Bio-efficacies of the herbicides decreased by around 2.0 times as the biochar application rate enhanced to 2.0%. The greatest GR50 values were obtained in the presence of 4.0% biochar in the soils and were about 7.0-8.5 folds, indicating the high capability of amended soil in the stabilization of the herbicides. The findings of this study can help to reduce imidazolinones' pollution and, in this way, prevent the threats of their residues to the environment.

Enhanced simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi) ions from aqueous solution using cassava root husk-derived biochar loaded with ZnO nanoparticles.

This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi). By conducting batch-mode experiments, it was concluded that 3% w/w was the best impregnation ratio for the modification of CRHB using ZnO-NPs, and was denoted as CRHB-ZnO3 in this study. The optimal conditions for heavy metal adsorption were obtained at a pH of 6-7, contact time of 60 min, and initial metal concentration of 80 mg L-1. The heavy metal adsorption capacities onto CRHB-ZnO3 showed the following tendency: Pb(ii) > Cd(ii) > As(iii) > Cr(vi). The total optimal adsorption capacity achieved in the adsorption of the 4 abovementioned metals reached 115.11 and 154.21 mg g-1 for CRHB and CRHB-ZnO3, respectively. For each Pb(ii), Cd(ii), As(iii), and Cr(vi) metal, the maximum adsorption capacities of CRHB-ZnO3 were 44.27, 42.05, 39.52, and 28.37 mg g-1, respectively, and those of CRHB were 34.47, 32.33, 26.42 and 21.89 mg g-1, respectively. In terms of kinetics, both the pseudo-first-order and the pseudo-second-order fit well with metal adsorption onto biochars with a high correlation coefficient of R 2, while the best isothermal description followed the Langmuir model. As a result, the adsorption process of heavy metals onto biochars was chemisorption on homogeneous monolayers, which was mainly controlled by cation exchange and surface precipitation mechanisms due to enriched oxygen-containing surface groups with ZnO-NP modification of biochar. The FTIR and EDS analysis data confirmed the important role of oxygen-containing surface groups, which significantly contributed to removal of heavy metals with extremely high adsorption capacities, comparable with other studies. In conclusion, due to very high adsorption capacities for metal cations, the cassava root husk-derived biochar modified with ZnO-NPs can be applied as the alternative, inexpensive, non-toxic and highly effective adsorbent in the removal of various toxic cations.

Acetylation of oil palm empty fruit bunch fiber as an adsorbent for removal of crude oil.

Removal of oil spillage from the environment is a global concern. Various methods, including the use of fibers as sorbents, have been developed for oil spill control. Oil palm empty fruit bunch (OPEFB) fiber is a plant biomass that may be acetylated by acetic anhydride using N-bromosuccinimide (NBS) as a catalyst; here, the extent of acetylation may be calculated in terms of weight percent gain (WPG). The modified fiber was used to remove Tapis and Arabian crude oils. The optimum time, temperature, and catalyst concentration were 4 h, 120 °C, and 3 %, respectively, and these parameters could achieve an 11.49 % increase in WPG. The optimized parameters improved the adsorption capacity of OPEFB fibers for crude oil removal. The acetylated OPEFB fibers were characterized by using Fourier transform infrared spectroscopy and field emission scanning electron microscopy to observe the functional groups available and morphology. Kinetic and isotherm studies were conducted using different contact times and oil/water ratios. The rate of oil sorption onto the OPEFB fibers can be adequately described by the pseudo-second-order equation. Adsorption studies revealed that adsorption of crude oil on treated OPEFB fiber could be best described by the Langmuir isotherm model.

Enhancing the hydrophobicity of mangrove bark by esterification for oil adsorption.

Oil spills generally cause worldwide concern due to their detrimental effects on the environment and the economy. An assortment of commercial systems has been developed to control these spills, including the use of agricultural wastes as sorbents. This work deals with raw and modified mangrove barks (Rhizophora apiculata), an industrial lignocellulosic waste, as a low cost adsorbent for oil-product-spill cleanup in the aquatic environment. Mangrove bark was modified using fatty acids (oleic acid and palmitic acid) to improve its adsorption capacity. The oil sorption capacity of the modified bark was studied and compared with that of the raw bark. Kinetic tests were conducted with a series of contact times. The influence of particle size, oil dosage, pH and temperature on oil sorption capacity was investigated. The results showed that oleic acid treated bark has a higher sorption capacity (2,860.00 ± 2.00 mg/g) than untreated bark for Tapis crude oil. A correlation between surface functional groups, morphology and surface area of the adsorbent was studied by Fourier transform infrared spectrum, field emission scanning electron microscopy images and Brunauer-Emmett-Teller analysis. Isotherm study was conducted using the Langmuir and Freundlich isotherm models. The result showed that adsorption of crude oil on treated mangrove bark could be best described by the Langmuir model.