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Waste activated sludge of crumb rubber industry (CRI-WAS) is discarded as waste from wastewater treatment processing. Therefore it is necessary to develop and innovate to convert the material becomes valuables and expected to be an economical adsorbent for metal ion remediation from wastewater. The ability of three types of adsorbents prepared from CRI-WAS for the removal of Zn(II) from aqueous solutions has been investigated. The XRF, BET, SEM-EDX, and FTIR analysis were conducted to characterize the PS (pure sludge), WS (washed sludge) and P600 (pyrolysis at 600 0 C) CRI-WAS types of adsorbents. In the batch system, experimental parameters were investigated, including solution pH, contact time, and adsorbent dose. The data were analyzed by analysis of variance (ANOVA) and a further test Duncan's New Multiple Range Test (DNMRT) at the 5% significance level. The results reveal that all types of adsorbent exhibited good sorption potential at pH 5.0. The P600 has largest adsorption capacity. The maximum adsorption capacity of the adsorbent for Zn(II) was found to be 10.276 mg g-1 , 11.042 mg g-1 and 64.169 mg g-1 for PS, WS and P600 CRI-WAS types of adsorbents respectively. The results showed that the adsorption isotherm data were fitted well by the Langmuir isotherm.

Esterification and trans-esterification reactions are an alternative solution for the production of biodiesel from Crude Palm Oil waste. The two previous studies show that the yield obtained was less than 80%. It is necessary to investigate the optimum condition of trans-esterification operation in biodiesel production from CPO waste. Variables used are temperature, time, ratio of molar triglyceride with methanol, and catalyst concentration. According to preliminary temperature treatment variations, it is determined that optimum temperature is 55°C. Meanwhile, the time treatment variations showed that optimum time is 60 minutes. For the ratio of molar triglyceride with methanol, it is determined that 1:10 is the optimum ratio. And last, for the experiment variations of NaOH concentrations it is discovered that the optimum concentration is 1.25%-b. And to conclude the research, the optimum condition for each variable was used where biodiesel’s yield can reach up to 96.67%.