Adsorption of Reactive Dyes from Wastewater Using Cationic Surfactant-modified Coffee Husk Biochar

Abstract

A solid agricultural waste, coffee husk, was applied as an adsorbent for reactive dye-polluted wastewater treatment. Coffee husk biochar was pyrolyzed at 450 °C and then chemically activated using 50% ZnCl2 solution. The surface of activated coffee husk biochar was modified using a cationic surfactant, Cetyltrimethylammonium bromide (CTAB), to create CTAB-modified coffee husk biochar (MCH), to improve reactive adsorption of anionic dyes from synthetic wastewater. The selected reactive dyes were reactive yellow 145 (RDY145), reactive red 195 (RDR195), and reactive blue 222 (RDB222). The adsorption kinetics fit well using a pseudo-second order model for all three dyes. The adsorption isotherms matched well with the Langmuir model .The removal efficiency of RDY145 (83.7%) was the highest, followed by RDR195 (71.1%) and RDB222 (59.6%). The amount of RDY145 adsorbed by MCH was about 9-fold that adsorbed by conventional activated carbon. Additionally, the solution pH had no effect on reactive dye removal efficiency using MCH.

Application of Biochar for Treating the Water Contaminated with Polar Halogenated Organic Pollutants

“…On the other hand, the sorption experiments using NaDCF and NaFLUFA were performed at different pH due to the low aqueous solubility of FLUFA at pH bellow 10. High removal efficiencies of A336/AlkBzMe 2 NCl mixtures with biochar even at high pH values are in agreement with our observation and the observation of Kosaiyakanon that the effect of pH is not crucial using separation method based on the formation of ion pairs [7,8,15].…”

“…4. Subsequently the high affinity of biochar to the produced ion pair R 4 N.DCF [15] (caused by decreasing of polarity of produced R 4 N.DCF ion pairs in comparison of NaDCF with subsequent increasing of their affinity to surface of tested biochar, as we were observed)…”

“…It has been observed, however, by Kosyiyakanon et al that the addition of R 4 NCls to the biochar enables the high efficiency of acid dyes removal even in a broad pH area from 3 to 9 [15]. This fact could be explained by the formation of low-soluble high-molecular ion pairs (dye-SO 3 NR 4 ) by the ion exchange reaction between the added R 4 NCl and -SO 3 Na groups bound in the structure of dye according to the scheme: dye-SO 3 Na + R 4 NCl -> NaCl + dye-SO 3 NR 4 (ion-pair).…”

“…Figure 10 illustrates that the sorption capacity (q) showed the following behavior: The worst removal capacity poses modified biocharAlkBzMe 2 NCl prepared by mixing biochar with aqueous AlkBzMe 2 NCl solution, subsequent washing with water, and drying [15] (for more details see Experimental section) probably due to the low concentration of AlkBzMe 2 N-cations immobilized on surface of prepared modified biochar. Figure 10 compared the effect of the addition of highly hydrophobic A336 added in different quantities to the hydrophilic 50% aq.…”

“…Here, q is the amount of adsorbed contaminant on the adsorbent at equilibrium (mg/g), q max is the maximum adsorption of contaminant on the adsorbent (mg/g), c is the residual contaminant concentration at equilibrium (mg/L), k L is the Langmuir constant related to the energy of adsorption (L/mg), k F is the Freundlich constant indicating the adsorption capacity, and n is the Freundlich exponent accounting for the adsorption intensity or the energetic heterogeneity of the adsorbing surface [15].…”