This study investigates the properties and potential application of Mg-PKS biochar composite for methylene blue solution (MB) adsorption. The Mg-PKS biochar composite was developed from palm kernel shell biochar via steam activation followed by MgSO4 treatment and carbonization. The effect of process parameters such as solution pH (4-10), contact time (30-90 min) and adsorbent dosage (0.1-0.5 g) were investigated via central composite design, response surface methodology. Results revealed that the Mg-PKS biochar composite has irregular shapes pore structure from SEM analysis, a surface area of 674 m2g-1 and average pore diameters of 7.2195 μm based on BET analysis. RSM results showed that the optimum adsorption of MB onto Mg-biochar composite was at pH 10, 30 min contact time and 0.5 g/100 mL dosage with a removal efficiency of 98.50%. In conclusion, Mg treatment is a potential alternative to other expensive chemical treatment methods for biochar upgrading to the adsorbent.

Sarawak is one of the world's largest exporter of sago flour, from which the processing leads to a generation of biowaste in a significant amount. Thus, utilization of the biowaste is crucial to create a zero-waste sago processing industry. In this work, the heavy metal adsorbent was prepared from sago activated sludge via microwave technology. Sago effluent was treated via an activated sludge process to produce biomass, followed by microwave pyrolysis and chemical activation using NaOH. The efficiency of the adsorbent for adsorption of Cr, Pb and Zn in aqueous solution was studied at pH 2, contact time (24 h), adsorbent dosage (0.2-1 g/50 mL), and initial concentration (5-25 mg/L). Physicochemical analyses showed that the adsorbent has an average pore size of 36.29 µm and BET surface area of 471.1 m 2 /g. The maximum removal of heavy metals was: Pb (89.8%), Cr (47.0%) and Zn (18.4%) at adsorbent dosage (1 g/50 mL), initial concentration (5 mg/L), mixing speed (150 rpm) and contact time (24 h). The Langmuir and Freundlich isotherm studies showed that Qe for Pb removal by sludge activated carbon was 3.202 × 10 -3 mg/g. The results indicated the potential application of sago activated carbon for the removal of heavy metals, especially Pb from wastewater. Further isotherm study for the occurrence of chemisorptions process could be beneficial, which at the same creating a zero-waste sago processing industry for sustainable technology.

The ability of coconut shell biochar (CSB) and acid-base modified coconut shell biochar (MCSB) for the removal of copper (Cu(II)) from aqueous solution is examined. The basic characteristics of CSB as well as MCSB such as proximate analysis, pH value, surface area, surface morphology and surface functional groups are investigated. The individual effect of initial concentration and contact time on the removal efficiency of Cu(II) by CSB and MCSB was determined using one variable at a time (OVAT) approach. In addition, the response surface methodology (RSM) approach is applied to determine the combined effects of variables (pH, contact time and particle size) on the removal efficiency of Cu(II) ion. The RSM results for the MCSB showed that Cu(II) maximum removal efficiency is 99.50% at pH 7, contact time of 60 min, and particle size of 0.60 mm, respectively. It can be concluded that MCSB has greater potential than CSB to be utilized as an adsorbent for Cu(II) removal in water bodies.

The use of agricultural by-products has been widely studied to develop effective and inexpensive adsorbent for heavy metal removal. In this study, sago (M.sagu) fly ash (FA) was chemically modified to afford an operational adsorbent for Pb (II) elimination from water. Chemical modification was carried out via acid-base treatment using NaOH and HCl. The chemically modified fly ash (MFA) was characterized via proximate, surface morphology, and functional groups' surface area analyses. The effects of adsorption parameters, namely, Pb (II) initial concentration, sorbent dosage and contact time on the eradication of Pb (II) by MFA was analyzed in batch experiments with Langmuir and Freundlich isotherms. Optimization of Pb (II) removal by MFA was studied via response surface methodology (RSM) approach. Results revealed that chemical modification has successfully enhanced the adsorptive properties of MFA (BET surface area: 231.4 m2/g, fixed carbon: 55.83%). MFA exhibits better Pb (II) removal efficiency (90.8%) compared to FA (63.6%) at the following adsorption condition: Pb (II) initial concentration (5 ppm), contact time (30 min) and agitation speed (150 rpm). The adsorption of Pb (II) by FA and MFA fitted well with Freundlich isotherm (R2>0.9). RSM study suggested that the optimum Pb (II) removal was 99.4% at the following conditions: Pb (II) initial concentration (20 ppm), contact time (2 h) and sorbent dosage (0.6 g/50 mL). The results concluded the potential optimum operational condition for Pb (II) removal from aqueous environment by MFA as a low cost adsorbent, at larger scale.