A Review on N-Doped Biochar for Oxidative Degradation of Organic Contaminants in Wastewater by Persulfate Activation

Abstract

The Persulfate-based advanced oxidation process is the most efficient and commonly used technology to remove organic contaminants in wastewater. Due to the large surface area, unique electronic properties, abundant N functional groups, cost-effectiveness, and environmental friendliness, N-doped biochars (NBCs) are widely used as catalysts for persulfate activation. This review focuses on the NBC for oxidative degradation of organics-contaminated wastewater. Firstly, the preparation and modification methods of NBCs were reviewed. Then the catalytic performance of NBCs and modified NBCs on the oxidation degradation of organic contaminants were discussed with an emphasis on the degradation mechanism. We further summarized the detection technologies of activation mechanisms and the structures of NBCs affecting the PS activation, followed by the specific role of the N configuration of the NBC on its catalytic capacity. Finally, several challenges in the treatment of organics-contaminated wastewater by a persulfate-based advanced oxidation process were put forward and the recommendations for future research were proposed for further understanding of the advanced oxidation process activated by the NBC.

Recent trends and economic significance of modified/functionalized biochars for remediation of environmental pollutants

“…Nonetheless, H 2 O 2 treatment was inefficient in methylene blue sorption 44 . After hydrogen peroxide activation of pinewood chip biochar, the sorption capacity of methylene blue decreased as the O-rich groups weakened the forces of delocalized π-interaction which was the core process for methylene blue sorption 38 . Apart from potassium permanganate which has a direct impact in enhancing cation-π interaction and O-containing functional groups in modified biochar 43 , 44 , hydrogen peroxide could also be applied as an activation agent 45 .…”

“…Potassium species such as K 2 CO 3 and K 2 O may be generated during modification due to the intercalation of potassium ions in the crystallite layer that creates condensed carbon structures. K 2 CO 3 and K 2 O may diffuse into the internal structure of the adsorbent matrix expand available pores and form new different pores of product 38 .…”

“…For instance, biochar derived from rice soaked with sodium hydroxide and consequently treated with methanol exhibited an improvement in surface attributes. Chemical mechanisms involved in char activation by methanol are esterification and then direct reaction between biochar carbonylic functional properties with methanol 38 . Methanol treated-adsorbent was enriched in hydroxyl and ester groups than un-activated char, which contributes to the EDA interaction formation between adsorbent surface and pollutants (pharmaceutic manufacturing wastewater, contaminated water, and soil) 54 .…”

“…Ball milling is a low-cost and eco-friendly technique that has been used for biochar modification through the improvement of key attributes such as pore structure, specific surface area, and enhancement of various surface functional groups than to the un-modified biochar 38 . Previously published literature has reported that several operational parameters could influence the physicochemical and catalytic/adsorptive characteristics of resultant biochar such as media mass ratio: biochar, dry or wet milling (without or with solvent), reaction time, and solvent characteristics, milling temperature and speed, reaction atmosphere and ball size distribution 98 .…”

Recent Progress on Semiconductor Heterogeneous Photocatalysts in Clean Energy Production and Environmental Remediation

“…Physical methods by using adsorption techniques can remove organic and inorganic pollutants under different operating conditions [24,25]. However, the incomplete removal of organic pollutants and the generation of waste products during treatment can lead to several challenges for the desired process [24,26]. On the other hand, despite the excellent selectivity, membrane separation technology often leads to high operating costs and increased energy consumption because of membrane fouling [24,27].…”