Removal of natural organic matter from water using chemically activated coffee husk

The presence of natural organic matter (NOM) in source water has posed many challenges for conventional water treatment facilities. Small organic acids, such as humic acid, present in NOM, have a high potential to influence the performance of water treatment processes. Uncontrolled application of agricultural chemicals leads to the simultaneous presence of toxic substances. In this work, batch adsorption experiments were conducted to examine the biosorption of HA onto chemically activated coffee husk. The biosorption process was studied as a function of operating conditions, such as contact time, pH of the solution, HA concentration, adsorbent dose and agitation speed parameters. Experimental results showed that the adsorption has an equilibrium time of 60 min with a maximum adsorption of 93.7%. The optimum pH for maximum HA adsorption was found to be 5.5, with a maximum adsorption of 94.3%. . As the dose of adsorbent increased from 1 to 25 g/L, the concentration of HA was observed to reduce from 10 to 1.67 mg/L which is below the WHO (World Health Organization) guideline value of 2 mg/L. The amount of HA adsorbed increased with increasing the initial adsorbent concentration from 0.5 to 20 mg/L. The adsorption kinetics well fitted the pseudo-second order model with the correlation coefficient R2 = 0.997 and Ks = 0.078. The experimental sorption equilibrium can be represented by the Langmuir isotherm (R2 = 0.998, SSE = 0.006). An average desorption capacity of 87.3% was observed. The study shows that chemically activated coffee husk can be a potential candidate to be used as a biosorbent in the removal of NOM from aqueous solutions.