Characterization and Ofloxacin Adsorption Studies of Chemically Modified Activated Carbon from Cassava Stem

Abstract

Cassava is a type of crop popular in Asian countries. It can be easily cultivated and grows to a mature plant in 9 months. Considering its availability, this work studied activated carbon based on cassava stem. Ofloxacin was chosen as the adsorbate, simulating the wastewater from the pharmaceutical industry. Cassava stem was ground into particles and heated to the activated state, 787 °C. The cassava-stem-activated carbon was further treated with the surface modifier, namely sodium hydroxide and zinc chloride, to study the improvement in ofloxacin adsorption. Prepared adsorbents were characterised using the SEM, FT-IR, XRD, DSC and TGA methods before being evaluated through batch adsorption, thermodynamic, and kinetic studies. The surface area analysis indicates that treatment of the activated carbon with NaOH and ZnCl2 increases the surface area due to the removal of organic content by the chemicals. Better ofloxacin adsorption of all activated carbon samples can be obtained with solutions at pH 8. An endothermic reaction was predicted, shown by higher ofloxacin adsorption at a higher temperature, supported by a positive value of ΔH° in the thermodynamic studies. The negative values of ΔG° revealed that adsorptions were spontaneous. The higher R2 values indicate that the adsorption process follows the pseudo-second-order equation of kinetic study. The maximum adsorption capacities are 42.37, 62.11, 62.89 and 58.82 mg/g for raw cassava stem (RC), cassava-stem-activated carbon (AC), NaOH-modified cassava-stem-activated carbon (NAC), and ZnCl2 modified cassava-stem-activated carbon (ZAC). The adsorption capacity is good compared to previous works by other researchers, making it a possible alternative material for the pharmaceutical industry’s wastewater treatment.

Adsorption of Levofloxacin onto Graphene Oxide/Chitosan Composite Aerogel Microspheres

“…As pH value increases, the repulsion is reduced and the adsorption capacity is correspondingly enhanced, with the greatest adsorption obtained at pH = 8. As reported in the literature [35,36], when the pH value is increased further, the negatively charged LOF has a weak electrostatic attraction with neutral -NH 2 (CS moiety), but has a repulsive interaction with negatively charged -COO -(GO moiety); thus, the adsorption of LOF will decrease at pH > 8. For this reason, higher pH values were not investigated and all further investigations were conducted at a pH of 8.…”

“…This relationship can be ascribed to the different charges of LOF and GO/CS microspheres at different pH values [15,25]. LOF presents as a zwitterionic molecule at pH values between 6 and 8, possesses a positive charge at pH < 6, and is negatively charged at pH > 8 [35,36]. Thus, extensive repulsion exists between positive LOF and -NH 3 + (CS moiety) when the pH < 6, reducing the adsorption of LOF at low pH values.…”

Effect of copper doping on the photocatalytic performance of Ni2O3@PC membrane composites in norfloxacin degradation

“…pH PZC signifies the pH at which the surface of the adsorbent or catalyst attains a state of net electrical neutrality. 63…”

Insights into the Roles of Surface Functional Groups and Micropores in the Sorption of Ofloxacin on Banana Pseudo-Stem Biochars

“…The following supporting information can be downloaded at: https://www. mdpi.com/article/10.3390/su16072629/s1, Table S1: Overview of literature data on sorption of OFL by different biochars [22,24,25,48,[64][65][66][67][68][69][70][71][72][73][74][75][76][77].…”