Enhanced nitrate removal by physical activation and Mg/Al layered double hydroxide modified biochar derived from wood waste: Adsorption characteristics and mechanisms

Investigation of the influence of crosslinking activation methods on the physicochemical and Cu(II) adsorption characteristics of cellulose hydrogels

“…9, the Langmuir model can describe the experimental data very well, which is signified by higher correlation coefficients (i.e., R 2 = ~1 and low SSE) than the Freundlich model. Moreover, the R L values of the Langmuir model fall within 0 < R L < 1 for the adsorption systems, indicating that the adsorption of Cu(II) ions onto WBH and MWH sorbents is favorable [76][77][78][79]. The n F of the Freundlich model shows a value between 1 and 10 for both systems, indicating the favorability of the process; this parameter is in good agreement with the R L value.…”

Adsorption of nitrate from interflow by the Mg/Fe calcined layered double hydroxides

“…When adsorbent dosage increased from 1.5 g/L to 2.5 g/L, the removal efficiency of nitrate significantly increased from 38.59% to 62.08%. This can be attributed to the increase in the effective active sites available for adsorption with the increasing adsorbent dosage (Wang et al 2021;Xu et al 2022). However, an increase in dosage of the adsorbent from 2.5 g/L to 5.5 g/L only slightly improved the removal efficiency from 62.08% to 72.96%.…”

“…Notably, the LDHs with special modifications may exhibit higher adsorption capacity. For example, Wang et al (2021) studied the nitrate adsorption with Mg/Al LDH loaded by activated biochar and found that the maximum adsorption capacity reached 156.84 mg/g. However, such modifications of LDH are usually accompanied by complex synthesis procedures and expensive costs.…”

“…The hydroxyl groups can adsorb nitrate with the formation of hydrogen bonds, and the metal ions (Mg 2þ , Fe 3þ ) can adsorb nitrate with the formation of metal-bonded bridges. Therefore, the formation of [Mg 1-x Fe x (OH) 2 ] (NO 3 ) x •nH 2 O in Equation ( 11) will be accompanied by the generation of new bonds, which indicates that the adsorption process involves chemical adsorption (Wang et al 2021). Moreover, CLDH may also adsorb the nitrate through an ion-exchange mechanism due to the negative charge of carbonates and hydroxyl groups, which may be another form of chemisorption (Wang et al 2021).…”

“…Therefore, the formation of [Mg 1-x Fe x (OH) 2 ] (NO 3 ) x •nH 2 O in Equation ( 11) will be accompanied by the generation of new bonds, which indicates that the adsorption process involves chemical adsorption (Wang et al 2021). Moreover, CLDH may also adsorb the nitrate through an ion-exchange mechanism due to the negative charge of carbonates and hydroxyl groups, which may be another form of chemisorption (Wang et al 2021). Overall, the Mg/Fe CLDH adsorbent can adsorb nitrate from aqueous solution via two mechanisms:…”