No abstract

In this study, modified biochar was adopted as an adsorbent for the nitrate removal in aqueous solutions. Raw material was impregnated in sulfuric acid (HSO, 1 mol/L) and sodium hydroxide (NaOH, 2 mol/L) separately and then prepared at 600 °C. After treated with acid, the BET specific surface area was much higher than that of unmodified and alkali-modified biochars. The low adsorption capacity and specific surface area of alkali-modified biochar may be due to the precipitate on the surface according to the results of XRD. In addition, the C-OH and C-H functional groups played a major part during adsorption progress. The batch experiments demonstrated that the acid-modified biochar exhibited a more excellent absorbability (12.75 mg/g) under the circumstance of neutral solution and room temperature. The maximum adsorption capacity of MSA-CC was 34.20 mg/g, which was about 2.4 times higher than that of the unmodified. Low pH value can provide positive charge conditions to enhance the adsorption capacity. Overall, the biochar with excellent pore structure and chargeable functional group can be a potential application for nitrate removal which was low cost and effective. After treated with acid, biochar could adsorb negative charge species like nitrate due to electrostatic interaction. Graphical abstract.

Biochar has good adsorption ability to various contaminants. In this work, peanut shell, corncob, cotton stalks, and crayfish shell were pyrolyzed under three temperatures (300, 450, 600 °C) to obtain biochars for the removal of Ni. The biochars were further modified with 2 mol/L NaS solution. Characterization results showed that the specific surface area and total pore volume of the modified biochars increased substantially. Among all the adsorbents, the modified corncob biochar (450 °C) showed the best Ni adsorption. The adsorption kinetics followed the Elovich model with an equilibrium time of 24 h. The maximum capacity of the modified biochar reached 15.40 mg/g. The adsorption process was affected by pH, temperature, and coexisting ions. Increasing pH (under 7) provided more adsorption sites which enhanced adsorption capacity. Experimental results also indicated that the main adsorption mechanism of Ni was ion exchange. Findings from this work suggest that modified biochar can be used as an effective adsorbent for the removal of Ni from wastewater. Graphical abstract ᅟ.

To develop low-cost adsorbents for aqueous nitrate, biochars were prepared from three types of agricultural residuals at different pyrolysis temperatures (300 °C, 450 °C, and 600 °C). The corncob biochar produced at 600 °C (CC600) was the best nitrate adsorbent of all the tested biochars. Characterization results showed that CC600 had good thermal stability, porous structure, and abundant surface functional groups. Findings from batch adsorption experiments demonstrated that CC600 showed relatively fast adsorption kinetics to nitrate in aqueous solutions. In addition, the Langmuir adsorption capacity of CC600 to nitrate was 14.46 mg/g, comparable to that of other biochar-based adsorbents. Therefore, CC600 showed promising potential to be used as a low-cost adsorbent for the treatment of nitrate in water.

Aluminum‐borate‐whiskers‐reinforced bismaleimide (BMI/Al18B4O33) composites were prepared, and the mechanical and thermal properties were investigated. Results show that the coupling agent used for surface treatment of whiskers has a great effect on the properties of these materials. Composites containing surface‐untreated whiskers, or silane‐compound‐KH 921‐treated whiskers, exhibited initially only a slight increase in the flexural strength when the whiskers weight content increased up to 5 wt%; thereafter, they showed a sharp decrease when the whiskers content was higher than 5 wt%. On the other hand, impact strength tests showed that the addition of the two kinds of whiskers decreased the impact strength of the composites. However, studies of the composite containing borate (BE4)‐treated whiskers showed that its flexural strength greatly increased with increasing whisker content. Moreover, the composite showed initially an increase in impact strength with a whisker content up to 10 wt%, then showing a slight decrease when the whisker content reached 15 wt%. Scanning electron microscopy observations revealed that the two coupling agents (KH 921 and BE4) employed in this work tend to change the fracture features of the composites from brittleness to that of ductile behaviour. Copyright © 2004 Society of Chemical Industry