The present study aimed to develop the activated carbon from fruit waste like sapota peel and to optimize the condition of developed activated carbon for complete removal of lead ions from the desired concentration of a lead solution. The activated carbon was prepared from sapota peel by using sulphuric acid. The physicochemical characterization of the obtained activated carbon was done for various parameters along with analysis of crystal nature (XRD) and structural morphology (SEM). The optimum conditions for adsorption were studied by altering pH (2-10), agitation speed (50-250 revolution per minute), temperature (10-60°C), adsorbent dose (0.02-0.14 g) and contact time (30-240 minutes). The optimized conditions necessary for complete removal of lead ions by the prepared adsorbent were pH - 5.5, agitation speed - 200 revolutions per minute, temperature - 60°C, time - 3 hours and adsorbent dose - 0.12 g. This study can be further helpful in designing the process of wastewater treatment for the removal of toxic metals from water particularly lead by adsorption.

For many years, especially in emerging nations like India, the environment has been threatened by the increased output of industrial wastes and heavy metal toxicity. The usage of inexpensive adsorbents has recently attracted a lot of attention in studies on the removal of heavy metals like nickel from industrial wastewater. The use of agro-based adsorbent is an alternative to conventionally used activated charcoal. In this research, adsorption experiments were carried out using agro-based adsorbent prepared from rice husk, wheat husk, and soybean husk to reduce nickel from industrial wastewater. The adsorption process is simple, economical, and effective is the most preferred method used for the removal of toxic metals like nickel from industrial wastewater. Adsorbents prepared from these husks can be effectively used for adsorption due to low cost & high availability. Characterization of agricultural material by various tests like XRF, proximate analysis, bulk density, and iodine number was conducted on agro-based adsorbents to know the co-relation between removal efficiency and adsorption capacity. The effect of turbidity and pH parameters on Ni removal efficiency is also studied. Results indicated that wheat husk adsorbent appeared to be the most effective for the adsorption of Ni from wastewater as compared to soybean husk and rice husk adsorbent. Wheat husk, soybean husk, and rice husk have removal efficiency in the range of 62.50 to 73.33. Composite absorbents CA-2 with the proportion of 50% wheat husk, 33% soybean husk, and 17% rice husk have 82.50% efficiency, and CA-3 has 80.83% efficiency in removing Nickel. Wheat husk adsorbent, CA-2, and CA-3 are more effectively and sustainably used for the treatment of industrial wastewater to remove heavy metals.

The aim of this work was to investigate the utilization of waste tire carbons as a low cost adsorbent for the removal of cadmium and lead ions from an aqueous solution. Surface functional groups would help in getting thorough knowledge about the adsorption capacity of the adsorbent. Thus, activated carbons were prepared from waste rubber tyres and characterized by means of field emission scanning electron microscopy, energy-dispersive X-ray and Fourier transform infrared spectroscopies. The FTIR spectra show that the adsorption peaks are shifted or disappeared and new peaks are formed which was due to the adsorption of lead and cadmium onto the adsorbent surface. It is evident that the characteristic adsorption peak of O-H stretching vibration was shifted from 3900 and 3075 cm-1 for lead and the asymmetrical stretching vibration at 3900 cm-1 was shifted to 3675 cm-1 for cadmium. This shift in peak indicates the interaction between metal ions and –OH groups of adsorbent due to the presence of alcohols, phenols, and carboxylic acid and which shows the decrease of free hydroxyl group content due to the interaction between lead cadmium with –OH groups of the adsorbent. SEM micrograph of adsorbent before adsorption is highly heterogeneous and the surface morphology of the adsorbent is rough. The pores were completely filled with the metal ions after the adsorption of lead and cadmium metals and the pores appear to be smooth. This observation indicates that the metal is adsorbed to the functional groups present inside the pores. From the XRD analysis, the CI index for raw, lead and cadmium loaded activated carbon of waste tyres were found to be 48.91%, 81%, and 54.9% respectively. These values clearly showed the increase in crystalline material present in the adsorbent after the adsorption of metal ions, which was due to the adsorption of metal ions onto the surface of the adsorbent.

To understand the features and best preparation of sludge activated carbon (SAC), and the pore structure, component, adsorption characteristics, and the yield rate of SAC, many tests have been carried out. The study illustrated that the pore structure was mostly mesopore and amorphous pore such as the ink bottle hole. In terms of different preparations to obtain SAC, the yield of SAC in sample No.1 achieved 88.09%. Using the preparation of ZnCl2 as an activator, the iodine adsorption value was significantly higher than other preparations. However, the content of quartz in sample No.1 achieved a maximum of 52.51%. Charcoal was detected in all samples except sample nos 9-12. The adsorption capacity of Cu(II) and Cd(II) reached a maximum of 600.02 mg.kg-1 and 383.2 mg.kg-1. The results showed an optimum preparation condition, which was by using the ZnCl2 as an activator, 2:1 as the impregnated ratio, 40% concentration in activator and at 400?C reaction temperature could create rich pore structure and charcoal inside.

This paper aims to review recent studies in preparing activated carbons from different types of agricultural wastes in Malaysia and how it can help Malaysia manage agricultural waste. It can be seen that most biomasses can be used as precursors to produce activated carbon for a wide range of pollutants and this adsorbent can be modified to optimally function depending on the types of pollutants. Under optimum dosages, modification through chemical activation using acidic, basic, or drying agents has significant effects on the selectivity of the analyte adsorption. The acidic activating agent causes the activated carbon to have negatively charged acid groups which enable it to adsorb cationic adsorbate while the basic activating agent causes the adsorbent to have a positive surface charge and enable it to adsorb anionic adsorbate.

The present study provides two naturally available sources for making adsorbents, waste tyres andBauhinia purpurea leaves, for the removal of lead from effluents. Equilibrium isotherms, kinetic modelsand thermodynamic studies were applied to observe the suitability of these adsorbents. Responsesurface methodology was adopted to investigate the influence of different process variables in leadadsorption process using both the adsorbents. For all the process parameters, the square and linearmodel terms were having significant effect than interactive model terms of lead adsorption processfor both the adsorbents. The interaction effects of the process variables of X1X2, X1X3, X2X3 and X2X4were highly influenced by the percentage removal of lead by using activated carbons prepared fromwaste tyres. To study the interaction effects of the process variables of X1X2, X2X3 and X2X4 were highlyinfluenced by the adsorption efficiency of lead by using activated carbons prepared from Bauhiniapurpurea leaves. All the squared terms, X1, X2, X3 and X4 show a negative influence on the adsorptionof lead on the two adsorbents. The interaction effect between process variables of X1X2 (p: 0.000, t:9.243), X1X3 (p: 0.03, t: 2.36), X2X3 (p: 0.000, t: 4.75) and X2X4 (p: 0.02, t: 2.71), were found to bestatistically significant and have positive effect on adsorption efficiency using ACWT as an adsorbent.The interaction effect between process variables of X1X2 (p: 0.000, t: 8.1049), X2X3 (t: 5.9657, p:0.000) and X2X4 (t: 5.9657, p: 0.000) was found to be statistically significant and positive effect onadsorption efficiency of lead, whereas other interactions were insignificant and did not influence theadsorption efficiency of lead using activated carbons of Bauhinia purpurea leaves adsorbent. Basedon the statistical approach, the experimental results were analysed by using ACWT and ACBPLadsorbents for the removal of lead and the optimum process conditions were as follows: pH: 4.98 and4.77, Ci: 140.01 mg/L and 105.7 mg/L, w: 0.12 g and 0.123 g, T: 314.46 K and 305.31 K and maximumadsorption efficiency of 95.64% and 95.55%, respectively.