Carbon dioxide (CO 2 ) is the main anthropogenic greenhouse gas contributing to global 29 warming, causing tremendous impacts on the global ecosystem. Fossil fuel combustion is the 30 main anthropogenic source of CO 2 emissions. Biochar, a porous carbonaceous material 31 produced through the thermochemical conversion of organic materials in oxygen-depleted 32 conditions, is emerging as a cost-effective green sorbent to maintain environmental quality by 33 capturing CO 2 . Currently, the modification of biochar using different physico-chemical 34 processes, as well as the synthesis of biochar composites to enhance the contaminant sorption 35 capacity, has drawn significant interest from the scientific community, which could also be 36 used for capturing CO 2 . This review summarizes and evaluates the potential of using pristine 37 and engineered biochar as CO 2 capturing media, as well as the factors influencing the CO 2 38 adsorption capacity of biochar and issues related to the synthesis of biochar-based CO 2 39 adsorbents. The CO 2 adsorption capacity of biochar is greatly governed by physico-chemical 40 properties of biochar such as specific surface area, microporosity, aromaticity, 41 hydrophobicity and the presence of basic functional groups which are influenced by 42 feedstock type and production conditions of biochar. Micropore area (R 2 = 0.9032, n=32) and 43 micropore volume (R 2 = 0.8793, n=32) showed a significant positive relationship with CO 2 44 adsorption capacity of biochar. These properties of biochar are closely related to the type of 45 feedstock and the thermochemical conditions of biochar production. Engineered biochar 46 significantly increases CO 2 adsorption capacity of pristine biochar due to modification of 47 surface properties. Despite the progress in biochar development, further studies should be 48 conducted to develop cost-effective, sustainable biochar-based composites for use in large-49 scale CO 2 capture.

Eutrophication of natural water is a universal problem. Nitrogen (N) and phosphorus (P) from agricultural runoff are the main sources of nutrient input, provided that emissions from industrial point sources (IPS) are under control. Therefore, it is of great environmental importance to reduce pollution associated with agricultural runoff as a means of regulating eutrophication levels in natural water. Numerous methods proposed for treating agricultural runoff can be classified into three categories: source control, process control, and end treatment. In this review, major technologies for N and P control from agricultural runoff are summarized along with discussion of newly proposed technologies such as biochar biomimetics and microbial catalyst. Because agricultural runoff (from farmlands to receiving waters) is a complicated pollution process, it is difficult to regulate the nutrients discharged via such process. This review will thus offer a comprehensive understanding on the overall process of agricultural runoff and eutrophication to help establish control strategies against highly complicated agricultural non-point sources.

An aqueous blend of monoethanolamine (MEA) and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) for CO2 absorption from simulated flue gas was investigated using a double stirred cell at a CO2 partial pressure of 15 kPa. It was found that the values of the enhancement factor (E) and the second-order reaction rate constant (k 2,mix) for CO2 absorption into mixed solution were higher than those into a single MEA aqueous solution with the same MEA concentration. k 2,mix and k 2, IL were found to be 3487.6 m3·kmol–1·s–1 and 1936.7 m3·kmol–1·s–1 at 303.15 K, respectively. The Arrhenius equation of CO2 absorption was also estimated. The results proved the assumption that [Bmim]BF4 had an active effect on the CO2 hydration. The diffusion and solubility of the absorbent in the solution were the limiting factors of the reaction.