ABSTRACT
Heavy metal contamination of water has become a global environmental burden, which has stirred up agitation worldwide. Fabrication of adsorbents utilizing either low cost, environment friendly materials or waste products can be helpful in remediating environmental pollution. The current study evolved around the synthesis of nanocomposites derived from such raw precursors like spent tea waste biochar, hydroxyapatite, and clays. In this context, two nanocomposites, namely manganese ferrite doped hydroxyapatite/kaolinite/biochar (TK-NC) and manganese ferrite doped hydroxyapatite/vermiculite/biochar (TV-NC), were synthesized followed by their employment for decontamination of heavy metals from aqueous media. TK-NC and TV-NC exhibited the crystallite sizes in the range of 2.55-5.94 nm as obtained by Debye Scherrer Equation and Williamsons-Hall equation The fabricated nanocomposites were characterized using FT-IR, SEM-EDX, and powder XRD. Batch adsorption studies were performed, and influence of different adsorption parameters (contact time, reaction temperature, solution pH, adsorbent dose, and initial adsorbate concentration) on metal adsorption was examined. Thermodynamic studies revealed that the adsorption of Cr(VI), Ni(II) and Cu(II) on TK-NC and TV-NC was endothermic (+ΔH°) and indicates disorderness (+ΔS°) at the solid-liquid interface owing to the strong affinity of metal ions with adsorbent. The heavy metal uptake selectivity followed the following decreasing order; Cr(VI) > Cu(II) > Ni(II) by both nanocomposites, with adsorption capacities falling in the range of 204.68-343.05 mg g-1. Several adsorption kinetic and isotherm models were applied to experimentally calculated data, which suggest favorable adsorption of Cr(VI), Ni(II) and Cu(II) by TK-NC and TV-NC from the system while obeying general-order kinetics and R-P adsorption model, conferring the transition in adsorption kinetics order and involvement of multiple adsorption process.
Subject(s)
Metals, Heavy , Water , Decontamination , Spectroscopy, Fourier Transform Infrared , DurapatiteABSTRACT
The aim of this study is to characterize the waste from the textile industry, to identify the sources and types of waste generation and to find out the economic and employment potential in this sector. Textile waste, its management, and the economic and employment potential in this sector are unrevealed facts in developing countries such as Pakistan. The textile industry is ranked first in export earning in Pakistan. Textile export of yarn and cloth from Faisalabad is US$3 billion per year. On average 161 325 people are employed in the textile sector in Faisalabad, of which 11 860 are involved in solid waste handling and management. The textile industries generate solid wastes such as fibre, metal, plastic and paper waste. A total of 794 209 kg day(-1) (289 886 285 kg year(-1)) solid waste is produced from this sector and purchased by cotton waste junkshop owners at US$125 027 day(-1) (US$45 634 855 year(-1)). Only pre-consumer textile waste is considered. Interestingly no waste is sent to landfill. The waste is first segregated into different categories/ types by hand and then weighed. Cotton waste is sold to brick kilns where it is used as an alternative fuel as it is cheaper than wood/coal. Iron scrap is sold in the junk market from where it is resold to recycling industries. Paper waste is recycled, minimizing the virgin material used for producing new paper products. Iron and plastic drums are returned to the chemical industries for refilling, thus decreasing the cost of dyes and decreasing the demand for new drums. Cutting rags are used for making different things such as ropes and underlay, it is also shredded and used as fillings for pillows and mattresses, thus improving waste management, reducing cost and minimizing the need for virgin material. As no system of quality control and no monitoring of subsequent products exist there is a need to carry out quality control and monitoring.
