Background (Metroxylon spp.) waste is an inexpensive and abundantly available material with the characteristics of a good adsorbent for treating dye from wastewater. We studied the effectiveness of alkali and acid modification in enhancing the adsorption capacity of sago waste. The untreated and treated adsorbent was characterized by FTIR, elemental analysis and BET surface area. The capacity of each adsorbent to adsorb MB was evaluated at different pH values, adsorbent dosage and initial dye concentrations and contact time. Results According to the results obtained, alkali treatment more than doubled the sorption capacity of sago waste by increasing the porosity, surface area and number of adsorption sites. The alkali-treated material also adsorbed significantly more than many known biosorbents. The effects of the initial concentration of methylene blue, solution pH and adsorbent dosage on methylene blue removal are reported. Equilibrium data were best represented by the Langmuir isotherm model with adsorption capacities of 83.5, 212.8 and 36.82 mg/g for untreated, potassium hydroxide-treated and phosphoric acid-treated sago wastes, respectively. The kinetics of adsorption were best described by a pseudo-second-order model (R 2 = 0.999). Conclusions The alkali treatment of sago waste demonstrates the use of a low-cost agricultural waste and a simple modification process to produce an effective adsorbent for removing cationic dye from wastewater.

The fast growth of the palm oil industry in Malaysia is associated with various waste products, namely the empty fruit bunches (EFB), which have a negative impact on the environment. Therefore, these wastes were utilized as a cheap raw material for the production of activated carbon (AC) with less energy consumption. Onestep steam pyrolysis was used to produce AC from oil palm empty fruit bunch fibers (EFBF) by varying the operating parameters of temperature, steam flow rate, and activation time using two-level full factorial experimental design (FFD). Ten samples of AC were prepared and the optimized production conditions were chosen based on the ability to adsorb and remove cadmium. Physical activation comprised of carbonization for 30 min using nitrogen gas (N 2 ), followed by activation with steam at different flow rates (2.0, 3.0, and 4.0 ml/min), temperatures (600, 750, and 900°C) and times (15, 30, and 45 min). The AC sample produced at an activation temperature of 900°C with a steam flow rate of 2.0 ml/min and activation time of 15 min was selected as the best adsorbent with a total yield of 21.7%. It had adsorbed more than 97% of total cadmium from aqueous solution within 2 min of the contact time. Characterization of EFBF-based AC by SEM and BET surface area analysis had shown a good-quality adsorbent with highly active sites and well-developed pores with BET surface area of 635.16 m 2 /g. Experimental results indicated that the prepared AC from EFBF provide a promising solution in water and wastewater treatment.